How to use this glossary. Search for any term, abbreviation, or contaminant name. Filter by category — Regulatory, Contaminant, Filtration, Measurement, Hardness, or Well Water. Every entry includes a Middle Tennessee context note explaining what the term means specifically for your utility’s water or your private well.
No terms match your search. Try a shorter term or clear the search.
A
Acid Neutralizer
FiltrationA water treatment system that raises the pH of acidic water using alkaline media — typically calcite (calcium carbonate) or corosex (magnesium oxide). As acidic water flows through the media bed, it dissolves small amounts of the media, neutralizing the acid and raising pH toward a neutral 7.0–8.0. Does not remove contaminants.
TN context: Critical pre-treatment step for Dickson County and Cheatham County well owners with pH below 6.5. Without correcting pH first, iron filters cannot oxidize dissolved iron effectively.
Activated Carbon (GAC — Granular Activated Carbon)
FiltrationA filtration media made from coconut shells, coal, or wood processed to create an extremely porous surface. Removes chlorine, chloramines (partial), TTHMs, HAAs, VOCs, pesticides, and taste and odor compounds through adsorption. Does not remove hardness, iron, nitrate, or bacteria.
TN context: The workhorse for all surface water utility customers. Nashville MWS (1.60 ppm chlorine avg), Franklin WD (bromodichloromethane 100x EWG), and Nolensville NCGUD (TTHMs 77.53 ppb LRAA) all require whole-house activated carbon as the foundation of any treatment system.
AIO Filter (Air Injection Oxidation)
FiltrationA well water treatment system that injects an air pocket into the top of a filter tank. As water passes through, dissolved ferrous iron contacts the air and oxidizes into solid ferric particles, which are then filtered out during backwash. Also removes hydrogen sulfide and manganese. No chemicals required.
TN context: The essential first step before the water softener for any Middle Tennessee well with iron above 1 ppm. Installing a softener before an AIO system fouls the resin permanently.
Aluminum
ContaminantA naturally occurring metal sometimes found in drinking water as a residual from aluminum sulfate (alum) used in water treatment as a coagulant, or from natural geological sources. EWG flags aluminum at levels above 0.05 mg/L. Long-term high exposure is associated with neurological concerns in some studies.
TN context: Detected in some Middle Tennessee utilities as a treatment residual. Reverse osmosis effectively removes aluminum from drinking water.
Arsenic
ContaminantA naturally occurring metalloid found in some groundwater formations. Long-term exposure significantly increases cancer risk. EPA MCL is 10 ppb. EWG’s health guideline is 0.004 ppb — 2,500 times more conservative. Has no taste, color, or odor.
TN context: Relevant for private wells in areas with Cambrian or Ordovician bedrock formations in Middle Tennessee. A one-time baseline arsenic test is recommended for any deep bedrock well. RO effectively removes arsenic.
Atrazine
ContaminantA widely used herbicide that leaches from agricultural land into surface water and groundwater. Disrupts hormone function. EPA MCL is 3 ppb. EWG’s health guideline is 0.1 ppb. Detected seasonally in surface water systems drawing from watersheds with significant agricultural activity.
TN context: Springfield Water System (Robertson County) showed atrazine at 0.260 ppb — 2.6x EWG’s health guideline — one of the distinctive contaminant findings in the Tennessee Water Authority guide series. Activated carbon effectively removes atrazine.
B
Bacteria (Coliform & E. coli)
ContaminantTotal coliform bacteria are used as an indicator of potential fecal contamination in water. E. coli (Escherichia coli) specifically indicates fecal contamination and is a direct health risk. Both are regulated under EPA’s Total Coliform Rule. Municipal water is disinfected to eliminate bacteria. Private wells are tested only when the owner arranges it.
TN context: The most serious risk for Middle Tennessee private well owners. Annual April testing for coliform and E. coli is essential across all nine Middle Tennessee counties. Spring rains, failing septic systems, and agricultural runoff all increase infiltration risk.
Barium
ContaminantA naturally occurring metal found in geological formations that can leach into groundwater. EPA MCL is 2 mg/L. High barium exposure is linked to cardiovascular effects and elevated blood pressure. Water softeners (ion exchange) effectively remove barium.
TN context: Detected in some Middle Tennessee groundwater. A standard water softener removes barium through the same ion exchange process used for hardness minerals.
Baseline Test
MeasurementA one-time comprehensive water test performed to establish the full contaminant profile of a water source — especially for private wells that have never been tested. Provides a reference point for all future testing and treatment decisions. Typically covers bacteria, nitrate, hardness, iron, pH, and a range of heavy metals and chemicals.
TN context: Essential for any Middle Tennessee homeowner on a private well who has never had the water tested, or who is purchasing a property with a well. Budget $150–$300 for a comprehensive panel from a TDEC-certified laboratory.
Backwash / Backwashing
FiltrationA maintenance cycle in tank-based water filters where water flow is reversed through the media bed to dislodge and flush out accumulated contaminants, sediment, and oxidized particles. Essential for AIO iron filters, carbon backwashing systems, softeners, and Greensand Plus systems. Typically programmed on a timer or by water usage volume.
TN context: Verify your AIO iron filter is backwashing on schedule quarterly. A missed backwash cycle allows accumulated iron to compact in the media bed, reducing effectiveness. Check the controller clock and drain line activity.
Birm Media
FiltrationA granular filter media that acts as a catalyst to oxidize dissolved ferrous iron into solid ferric particles using dissolved oxygen in the water. Low cost, no chemicals required. Requires pH above 6.8 and adequate dissolved oxygen. Effective for moderate iron levels (under 5 ppm) in well-oxygenated, neutral to alkaline water.
TN context: A cost-effective option for moderate-iron wells in Wilson County and neutral-pH parts of Williamson County. Not suitable for Dickson or Cheatham County acidic wells without pH correction first.
Bromodichloromethane (BDCM)
ContaminantOne of the four trihalomethane (TTHM) compounds formed when chlorine reacts with organic matter in water. The most commonly elevated individual TTHM in Middle Tennessee utilities. Associated with increased cancer risk and adverse reproductive outcomes at elevated concentrations. EWG health guideline is 0.06 ppb.
TN context: Franklin Water Department tested at 6.01 ppb (100x EWG). Brentwood’s Gateway Water (NCGUD area) tested at 8.70 ppb (145x EWG) — the highest bromodichloromethane reading in the Tennessee Water Authority guide series. Whole-house activated carbon effectively reduces BDCM.
C
CCR (Consumer Confidence Report)
RegulatoryAn annual water quality report that every EPA-regulated public water system must deliver to customers by July 1 each year. Reports the source water, detected contaminants, their measured levels, EPA limits (MCLs), and any violations. Private well owners do not receive CCRs — they are responsible for their own testing.
TN context: Tennessee Water Authority verifies CCR data for all 17 Middle Tennessee utilities covered in our city guides. Nashville MWS published their 2025 CCR (covering 2024 data) in May 2026. You can request a copy from your utility or find it on the EPA’s ECHO database.
Calcite
FiltrationCalcium carbonate media used in acid neutralizer filter tanks to raise the pH of acidic water. As acidic water flows through the calcite bed, it slowly dissolves the media, neutralizing acidity and raising pH. Also adds a small amount of hardness to the treated water as a byproduct. Requires periodic media replenishment (typically once or twice per year).
TN context: Required pre-treatment for Dickson County and parts of Cheatham County where chert and shale geology produces acidic groundwater. Without raising pH above 6.8 first, iron filters cannot function correctly.
Catalytic Carbon
FiltrationAn enhanced form of activated carbon with catalytic properties that accelerate chemical reactions in addition to adsorption. Removes chlorine AND chloramines far more effectively than standard GAC, plus hydrogen sulfide, iron, manganese, VOCs, TTHMs, and HAAs. The preferred whole-house carbon for utilities using chloramine disinfection.
TN context: The upgrade from standard GAC for Nashville MWS customers (which uses chloramine in parts of its system). Also the preferred media for Middle Tennessee well water with both iron and sulfur — common in Dickson and Williamson County wells.
Chloramine
ContaminantA disinfectant formed by combining chlorine with ammonia. Used by many utilities as a secondary disinfectant because it produces lower TTHM levels than free chlorine and persists longer in distribution systems. Standard activated carbon (GAC) removes chloramine slowly and inefficiently; catalytic carbon is required for effective chloramine removal.
TN context: Used in parts of the Nashville Metro Water Services distribution system. If you notice that your standard carbon filter is exhausting faster than expected, chloramine may be the cause. Verify your utility’s disinfection method with your CCR.
Chlorine (Free Residual)
ContaminantA disinfectant added to municipal water to kill bacteria and pathogens. EPA requires a detectable residual throughout the distribution system. “Free residual chlorine” is the amount remaining in the water at your tap. While effective at preventing microbial contamination, residual chlorine reacts with organic matter to form TTHMs and HAAs.
TN context: Nashville MWS averages 1.60 ppm chlorine (highest avg, 2025 CCR). Smyrna WS highest RAA: 1.53 ppm. Standard activated carbon effectively removes free chlorine but not chloramines. The chlorine taste most Middle Tennesseans notice from city water is entirely removed by a properly maintained carbon filter.
Chromium-6 (Hexavalent Chromium, Cr-VI)
ContaminantA toxic form of the metal chromium associated with cancer, liver damage, and reproductive harm. A known carcinogen. EPA’s current total chromium MCL is 0.1 mg/L (100 ppb) — a standard EWG considers dangerously outdated. EWG’s health guideline for chromium-6 is 0.02 ppb. California has set a specific chromium-6 limit of 10 ppb.
TN context: Murfreesboro MWRD detected chromium-6 at 0.169 ppb — 8.5x EWG’s health guideline. Reverse osmosis effectively removes chromium-6. Standard carbon filters do not. Look up your utility on EWG’s chromium-6 map →
Coagulation / Flocculation
MeasurementThe first stages of conventional water treatment. Coagulation involves adding chemicals (typically alum or ferric sulfate) that cause small suspended particles to clump together (floc). Flocculation is the gentle mixing that allows those clumps to grow large enough to settle out. Both steps remove turbidity, sediment, and some pathogens before filtration.
TN context: Used at Nashville’s Harrington and Omohundro plants (Cumberland River), Franklin’s Harpeth River plant, and all surface water treatment facilities in Middle Tennessee. Explains why aluminum sometimes appears as a treatment residual in finished water.
Compliance / Violation
RegulatoryA utility is in compliance when all detected contaminants remain below EPA Maximum Contaminant Levels (MCLs) and all monitoring and reporting requirements are met. A violation occurs when a contaminant exceeds its MCL, when required testing is not performed, or when public notification requirements are not met. Violations must be reported to customers.
TN context: All major Middle Tennessee utilities covered in our city guides were in full compliance with no health violations in 2025. Exceeding EWG guidelines is not a violation — EWG limits are more conservative than EPA’s legally enforceable MCLs.
D
DBP (Disinfection Byproducts)
RegulatoryChemicals formed when disinfectants (primarily chlorine) react with naturally occurring organic matter in source water. The two main regulated DBP groups are TTHMs (Total Trihalomethanes) and HAA5s (Haloacetic Acids). DBPs are the most commonly exceeded EWG health guideline in surface water utilities across the United States.
TN context: All surface water utilities in Middle Tennessee produce disinfection byproducts. The higher the organic matter in the source river (Harpeth River in Franklin, Stones River in Murfreesboro), the higher the DBP formation potential when chlorine is added.
Detection Limit / Not Detected (ND)
MeasurementThe lowest concentration of a contaminant that a laboratory test can reliably identify. “Not detected” (ND) on a water test result does not necessarily mean zero — it means the contaminant was below the instrument’s detection threshold. Different labs have different detection limits for the same contaminant.
TN context: Nashville MWS reported PFAS as “not detected” in 2024. This means all tested PFAS compounds were below the lab’s detection threshold — a positive result compared to Spring Hill WD and Milcrofton UD where PFOA was detected above EWG guidelines.
Dibromochloromethane (DBCM)
ContaminantOne of the four trihalomethane (TTHM) compounds. Forms when chlorine reacts with organic matter in water, particularly in water with higher bromide concentrations. Associated with liver, kidney, and neurological effects at elevated levels. One of the four TTHMs measured in the LRAA calculation reported in every utility’s CCR.
TN context: Present in all chlorinated surface water utilities in Middle Tennessee. Reported as part of the total TTHM figure in CCRs. Whole-house activated or catalytic carbon effectively reduces dibromochloromethane.
Drinking Water Standards (SDWA)
RegulatoryThe Safe Drinking Water Act (SDWA) is the primary federal law protecting public drinking water in the United States, enacted in 1974 and amended multiple times. It authorizes EPA to set MCLs and treatment standards for public water systems. Private wells serving fewer than 25 people are not regulated under SDWA.
TN context: All public water systems in Tennessee are regulated by TDEC (Tennessee Department of Environment and Conservation) under the authority delegated from EPA’s SDWA program. Private well owners are outside this regulatory framework entirely.
Dual-Tank Softener
FiltrationA water softener system with two resin tanks that alternate service so one is always on duty while the other regenerates. Provides continuous soft water with no hardness breakthrough during regeneration cycles. More expensive than single-tank systems but valuable for households with very high water demand or extremely hard water where single-tank recovery time is insufficient.
TN context: Relevant for large households in Murfreesboro, Smyrna, or La Vergne at 10–14 GPG, or for deep Williamson County well water at 15–20+ GPG where a single tank’s regeneration cycle might not keep up with demand.
E
EWG (Environmental Working Group)
RegulatoryA nonprofit research and advocacy organization that maintains the EWG Tap Water Database, covering nearly 50,000 U.S. water utilities. EWG sets its own health guidelines based on peer-reviewed studies at the lowest levels where health effects may begin — significantly more conservative than EPA’s MCLs, which balance health with technical and economic feasibility. EWG guidelines are not legally enforceable.
TN context: Tennessee Water Authority uses EWG data for all 17 city guides. Water above EWG guidelines is not illegal — but EWG argues EPA’s older standards don’t reflect current science. Every contaminant card in our guides shows both EPA limits and EWG health guidelines.
EWG Tap Water Database →
EPA (Environmental Protection Agency)
RegulatoryThe federal agency responsible for setting and enforcing drinking water standards in the United States under the Safe Drinking Water Act. Sets MCLs (Maximum Contaminant Levels) and MCLGs (Maximum Contaminant Level Goals) for regulated contaminants. Delegates primary enforcement authority to states — in Tennessee, to TDEC.
Effluent
MeasurementWater that has passed through a treatment system or filter and exits as the treated output. In water quality testing, “effluent” refers to the water leaving a treatment plant or filter unit. The opposite of “influent” (water entering the system). Performance Data Sheets report both influent and effluent contaminant concentrations to show reduction percentages.
F
Ferric Iron (Red-Water Iron)
ContaminantIron that has already oxidized — water looks orange, yellow, or rusty directly at the tap. Unlike ferrous iron which is dissolved and invisible, ferric iron is in particulate form. Often indicates surface water infiltration through a damaged well casing, a shallow water table, or iron oxidizing inside the well or pipes.
TN context: More common in older rural wells across Robertson and Cheatham Counties. A sediment or Birm filter captures ferric iron particles. If water is orange at the tap, a well casing inspection is also recommended.
Ferrous Iron (Clear-Water Iron)
ContaminantDissolved iron that is invisible at the tap — water looks crystal clear when drawn — but oxidizes and turns orange on contact with air, bleach, or oxygen in plumbing fixtures. The most common type of iron problem in Middle Tennessee well water. Causes orange staining on toilets, laundry (worsened by bleach), and showerheads.
TN context: The most prevalent iron type across Williamson, Maury, Dickson, Robertson, and Cheatham County wells. If your water looks clear but everything turns orange, ferrous iron is almost certainly the cause. An AIO iron filter eliminates the problem at the source.
Fluoride
ContaminantAdded to most public water supplies for dental health benefits at approximately 0.7 mg/L (per current HHS recommendation). EPA MCL is 4.0 mg/L for health; secondary limit is 2.0 mg/L for cosmetic effects (dental fluorosis). Naturally occurring fluoride from geological formations can exceed these limits in some private wells. Reverse osmosis effectively removes fluoride.
TN context: All major Middle Tennessee surface water utilities add fluoride as a public health measure. Some private well owners in mineral-rich geological areas may have naturally elevated fluoride. Test private wells for fluoride baseline if the well draws from deep bedrock.
Flow Rate (GPM — Gallons Per Minute)
RegulatoryThe volume of water passing through a filter, pipe, or system per minute. Critical for correctly sizing whole-house filtration systems. A filter rated for 6 GPM will cause noticeable pressure drops in a four-bedroom home at peak morning usage. Undersized filters are one of the most common installation mistakes.
TN context: Nashville area single-family homes should target a minimum 8 GPM flow rate for the whole-house filter to avoid pressure complaints during peak hours when multiple fixtures run simultaneously.
G
GPG (Grains Per Gallon)
MeasurementThe standard unit used by water treatment equipment manufacturers to measure water hardness. One grain per gallon equals 17.1 mg/L (milligrams per liter / ppm). To convert your utility’s mg/L hardness to GPG, divide by 17.1. Water softeners, test kits, and sizing guides all use GPG.
TN context: Nashville 5.9 GPG (100.5 mg/L) · Clarksville 5.67 GPG (97 mg/L) · Franklin 7.9 GPG (135 mg/L) · Smyrna/Murfreesboro est. 10–14 GPG · Rural Williamson Co. wells 15–20+ GPG. Your CCR reports in mg/L; your softener is sized in GPG. You need both numbers.
GPD (Gallons Per Day)
MeasurementThe daily water production capacity of a reverse osmosis membrane. Common residential RO membranes are rated 50, 75, or 100 GPD. A 50 GPD membrane producing filtered water at about 2 gallons per hour may not keep up with a large household’s daily drinking and cooking demand if the storage tank is undersized.
TN context: Families of 4+ in Middle Tennessee should look for a 75–100 GPD membrane and at least a 4-gallon storage tank, or a tankless RO system, to avoid running out of filtered water during peak usage.
Grain Capacity (Softener Sizing)
FiltrationThe total amount of hardness a water softener resin bed can remove before needing to regenerate, measured in grains. Common residential capacities: 24,000, 32,000, 48,000, and 64,000 grains. Correct sizing = daily water usage (gallons) × water hardness (GPG) × days between regenerations (typically 3–7).
TN context: A 32,000-grain softener is typically appropriate for a family of four at Nashville’s 5.9 GPG. At Murfreesboro’s estimated 12 GPG, the same family needs a 48,000–64,000 grain system. At Williamson County well water hardness of 15–20 GPG, a 64,000+ grain system is standard.
Greensand Plus
FiltrationA manganese dioxide-coated filter media for iron, manganese, and hydrogen sulfide removal. More powerful than Birm media and handles higher contaminant concentrations and a broader range of water conditions. Requires chemical regeneration with potassium permanganate or chlorine, adding to operating cost and maintenance complexity.
TN context: The step up from Birm for wells with iron above 5 ppm or combined iron-manganese-sulfur issues. More common in deeper Rutherford County and Maury County wells. The chemical regeneration requirement is the main trade-off vs. a chemical-free AIO system.
H
HAA5 (Haloacetic Acids)
ContaminantA group of five haloacetic acid compounds (mono-, di-, and trichloroacetic acid, plus mono- and dibromoacetic acid) formed when chlorine reacts with organic matter in water. Regulated together as HAA5. EPA MCL is 60 ppb (LRAA). EWG’s health guideline is 0.1 ppb — 600 times more conservative. Associated with cancer and reproductive risks at elevated levels.
TN context: Present in all chlorinated surface water utilities in Middle Tennessee. Nolensville NCGUD: HAA5 36.55 ppb LRAA. Franklin WD: above EWG guidelines. Whole-house activated or catalytic carbon reduces HAA5 compounds.
Hardness (Water Hardness)
HardnessThe concentration of dissolved calcium and magnesium ions in water, expressed in GPG (grains per gallon) or mg/L (milligrams per liter). Hard water causes scale buildup on fixtures and inside pipes and appliances, reduces soap lathering efficiency, and shortens appliance lifespans. Middle Tennessee sits on extensive limestone geology, producing some of the hardest water in the eastern United States.
TN context: Soft <1.0 GPG · Slightly Hard 1.0–3.5 GPG · Moderately Hard 3.5–7.0 GPG · Hard 7–10 GPG · Extremely Hard 10.5+ GPG. Nashville 5.9 GPG. Franklin 7.9 GPG. Murfreesboro/Smyrna est. 10–14 GPG. Rural wells 12–20+ GPG.
Hard Water Guide for Middle Tennessee →
Hydrogen Sulfide (H₂S)
ContaminantA dissolved gas produced by sulfur-reducing bacteria in oxygen-depleted groundwater. Produces a distinctive rotten egg odor detectable even at very low concentrations (as low as 0.05 ppm). Not a direct health hazard at typical household levels but aggressively corrodes copper plumbing, fixtures, and pump components.
TN context: Common in deeper wells across Williamson, Montgomery, and Dickson Counties. An AIO iron filter with catalytic carbon media addresses both H₂S and iron simultaneously. Test to confirm H₂S vs. sulfate-reducing bacteria — treatment differs for each.
Well Head / Well Casing
Well WaterThe visible above-ground portion of a well and the steel or PVC pipe (casing) that extends from the surface down into the aquifer. The well cap seals the top of the casing against surface water infiltration, insects, and debris. A damaged or improperly sealed well cap is one of the most common causes of bacterial contamination in private wells.
TN context: Inspect your well head monthly. Verify the cap is tight, undamaged, and that surface drainage flows away from the casing. Robertson and Maury County well owners should check for ant or rodent activity, which can damage electrical connections and the cap seal.
I
Influent
MeasurementWater entering a treatment system or filter unit before processing. Performance Data Sheets show influent (incoming) and effluent (outgoing) contaminant concentrations to demonstrate actual reduction percentages achieved by a filter system.
Ion Exchange (Water Softening)
FiltrationThe process by which a resin bed captures calcium and magnesium ions (hardness) and releases sodium ions in exchange. The foundation of traditional water softening. After processing a set volume of water, the resin regenerates using a salt (sodium chloride) brine solution to recharge the exchange capacity. Simple version: Imagine thousands of tiny beads inside the softener tank. Each bead is holding a sodium atom like a hand holding a coin. When hard water flows past, the calcium and magnesium atoms — which stick more strongly — grab onto the beads and push the sodium atoms off into the water. The calcium and magnesium stay trapped on the beads; the water flows out soft. When all the beads are full of calcium and magnesium, the softener flushes them with salty brine. The salt knocks the calcium off, washes it down the drain, and resets the beads back to holding sodium — ready to go again.
TN context: The only proven method for substantially reducing water hardness above 7 GPG. Salt-free conditioners (TAC/SP3) do not perform ion exchange and do not reduce GPG hardness readings — an important distinction for Murfreesboro, Smyrna, and La Vergne customers at estimated 10–14 GPG.
Iron / Manganese
ContaminantTwo naturally occurring metals commonly found together in Middle Tennessee groundwater. Iron produces orange/rust staining; manganese produces black or dark brown staining. EPA secondary limits: iron 0.3 ppm, manganese 0.05 ppm. Both are aesthetic concerns at typical levels but manganese has an EPA health advisory of 0.1 mg/L for children based on neurological effects.
TN context: The defining water quality challenge for Middle Tennessee private well owners. Iron is common across all nine Middle Tennessee counties. A certified water test confirming both iron and manganese PPM levels is required before selecting a filter — treatment media for each differ.
K
KDF Media (Kinetic Degradation Fluxion)
FiltrationA copper-zinc alloy filtration media that removes chlorine, hydrogen sulfide, iron, and some heavy metals (lead, mercury) through redox (oxidation-reduction) reactions. Also inhibits the growth of bacteria, algae, and fungi inside filter housings. Typically blended with activated carbon rather than used alone. Does not remove hardness, nitrate, or organic chemicals on its own.
TN context: Commonly blended with carbon in whole-house filter tanks. The bacteria-inhibiting property is valuable in filter tanks that can grow biofilm in humid Middle Tennessee conditions.
L
Lead
ContaminantA toxic heavy metal with no safe level of exposure, especially for children. EPA’s action level is 15 ppb. The MCLG is zero. Lead enters water not from source water or treatment, but primarily from lead service lines, lead solder (used in plumbing before 1986), and brass fixtures. Utilities must replace lead service lines under the EPA’s Lead and Copper Rule revisions.
TN context: La Vergne WS completed its Lead Service Line Inventory (LSLI) in 2025, confirming no lead service lines in its distribution system. Nashville MWS and other utilities are in various stages of LSLI completion. For homes built before 1986, lead solder inside the home is a potential concern — NSF/ANSI 53 certified filters for lead are recommended.
LRAA (Locational Running Annual Average)
RegulatoryThe compliance calculation method for TTHMs and HAA5s. The LRAA is the average of a sampling location’s last four quarterly test results. A utility is in violation only if the LRAA exceeds the MCL (80 ppb for TTHMs, 60 ppb for HAA5) — not if a single quarterly test exceeds it. This can mask high seasonal peaks in individual quarters.
TN context: Nolensville NCGUD LRAA for TTHMs: 77.53 ppb — the highest in our guide series, just under the 80 ppb MCL limit. Some individual quarterly tests at that utility may have been significantly higher. Always note whether a CCR reports an LRAA or a single-quarter result.
LSLI (Lead Service Line Inventory)
RegulatoryRequired under EPA’s revised Lead and Copper Rule, utilities must conduct a full inventory of all service lines to identify lead lines requiring replacement. The inventory covers both utility-owned lines and privately owned lines from the meter to the home. Utilities must publish their LSLI results and establish replacement schedules.
TN context: La Vergne WS completed its LSLI and confirmed zero lead service lines in its system (2025 CCR). Nashville MWS and other Middle Tennessee utilities are in varying stages of LSLI completion as of 2026.
M
Manganese
ContaminantA naturally occurring metal that produces black or dark-brown staining on fixtures, dishwashers, and laundry — distinct from iron’s orange staining. EPA secondary limit is 0.05 mg/L. EPA health advisory for children is 0.1 mg/L based on neurological effects. Often found alongside iron in Middle Tennessee groundwater but requires different treatment media than iron alone.
TN context: Black staining on fixtures is the diagnostic indicator. Common in deeper Rutherford, Wilson, and Williamson County wells. AIO systems with manganese-specific media (Birm, Greensand Plus, manganese dioxide) are required. Always test for manganese separately from iron before purchasing any iron filter.
MCL (Maximum Contaminant Level)
RegulatoryThe legally enforceable limit set by EPA for a contaminant in public drinking water. If a utility’s water exceeds an MCL, it is in violation and must notify customers and take corrective action. MCLs are set as close to the MCLG as feasible, considering available treatment technologies and cost.
TN context: All major Middle Tennessee utilities were within all MCLs in 2025. Tennessee Water Authority reports both MCL and EWG health guidelines because EWG guidelines are often significantly more conservative than MCLs — reflecting what current science suggests is optimal vs. what is legally required.
MCLG (Maximum Contaminant Level Goal)
RegulatoryThe non-enforceable health goal set by EPA at the level where no known or anticipated adverse health effects occur with an adequate margin of safety. For many contaminants, the MCLG is lower than the enforceable MCL. For lead, the MCLG is zero — meaning no level of lead in drinking water is considered safe — but the MCL action level is 15 ppb.
mg/L (Milligrams Per Liter)
MeasurementThe unit used in Consumer Confidence Reports and laboratory test results to express contaminant concentrations. Equivalent to ppm (parts per million) for practical water quality purposes. To convert water hardness from mg/L to GPG (used by water softener manufacturers), divide by 17.1.
TN context: Nashville MWS CCR reports hardness as 100.5 mg/L ÷ 17.1 = 5.9 GPG. Franklin WD CCR reports 135.1 mg/L = 7.9 GPG. Always check the units when comparing a utility report to a filter specification sheet.
N
NSF/ANSI Certification (NSF International)
RegulatoryVoluntary third-party certifications from NSF International verifying that water filters perform as claimed and materials won’t leach harmful substances. Key standards: NSF/ANSI 42 (aesthetic — chlorine, taste, odor), NSF/ANSI 53 (health effects — lead, cysts, VOCs), NSF/ANSI 58 (reverse osmosis systems), NSF/ANSI 401 (emerging contaminants — pharmaceuticals, BPA, DEET). Costs manufacturers $10,000–$100,000+ per product.
TN context: NSF certification is a useful baseline but not the only metric for choosing a filter. Many high-quality systems aren’t certified due to cost. Always ask for the Performance Data Sheet in addition to certification numbers. See our Certifications Guide.
Nitrate
ContaminantA chemical compound from agricultural fertilizers, septic system effluent, and natural decomposition that leaches into groundwater and surface water. EPA MCL is 10 mg/L (10 ppm). Acutely dangerous for infants under 6 months (methemoglobinemia / “blue-baby syndrome”). No taste or smell. Never boil — boiling concentrates nitrate rather than removing it. Only RO or dedicated anion exchange resin removes nitrate.
TN context: High risk in agricultural-area wells across Maury County (row crops and livestock), Robertson County (tobacco and row crops), Wilson County, and Montgomery County. Annual spring testing is essential. Use RO-filtered water for all infant formula if nitrate is detected.
Nanoplastics / Microplastics
ContaminantTiny plastic particles found in both tap and bottled water. Nanoplastics are smaller than microplastics (under 1 micron) and can penetrate biological barriers. A 2024 study found bottled water may contain 100x more nanoplastic particles per liter than previously estimated — up to 240,000 per liter. Reverse osmosis effectively removes both micro and nano plastic particles.
TN context: One of the key arguments for RO over bottled water. Our bottled vs. filtered water guide covers this in detail. RO membranes remove essentially all plastic particles from water — bottled water (even premium brands) does not.
Bottled vs. Filtered Water Guide →
O
NOM (Natural Organic Matter)
MeasurementNaturally occurring carbon-based compounds from decaying plant and animal material that are present in surface water sources. NOM is not directly harmful but reacts with chlorine during disinfection to form TTHMs and HAA5s. Higher NOM concentrations in the source river mean higher disinfection byproduct formation in the treated water.
TN context: The Harpeth River (Franklin), Stones River (Murfreesboro), and Duck River (Spring Hill/Columbia) all have higher organic loading than the Cumberland River (Nashville), which partly explains why Franklin and Murfreesboro utilities show higher TTHM concentrations.
P
pCi/L (Picocuries Per Liter)
MeasurementThe unit used to measure radioactivity in water — picocuries per liter. Used for radium, radon, uranium, and other radioactive contaminants. EPA MCL for combined radium-226 and radium-228 is 5 pCi/L. EWG’s health guideline is 0.05 pCi/L — 100 times more conservative.
TN context: Hendersonville Water System detected radium-226 and radium-228 combined above EWG guidelines — a distinctive finding unique in our guide series. Reverse osmosis effectively removes radium from drinking water.
PDS (Performance Data Sheet)
MeasurementA technical document produced by a filter manufacturer or independent testing laboratory showing measured contaminant reduction results under laboratory conditions. Includes inlet and outlet contaminant concentrations, flow rate used in testing, test water chemistry, and performance at end-of-life. More informative than certification alone. Any reputable manufacturer makes their PDS freely available.
TN context: Tennessee Water Authority recommends always requesting a PDS before purchasing any water treatment system. If a company cannot provide one and only references its certification number, ask why. Reputable manufacturers support their claims with data.
Certifications & PDS Guide →
PFAS (Per- and Polyfluoroalkyl Substances)
ContaminantA group of thousands of synthetic chemicals used in non-stick cookware, food packaging, firefighting foam, and industrial processes. Called “forever chemicals” because they do not break down in the environment or the human body. Associated with cancer, thyroid disruption, immune system effects, and reproductive harm. EPA set new MCLs for PFOA and PFOS at 4 parts per trillion in 2024 — the most protective federal drinking water limits ever established. Reverse osmosis and PFAS-specific GAC effectively remove most PFAS compounds.
TN context: Nashville MWS: zero PFAS detected (2024). Milcrofton UD and Spring Hill WD: PFOA detected above EWG guidelines. NSF/ANSI 58 certification with PFOA specifically listed is the key filter requirement for Spring Hill area customers.
PFOA (Perfluorooctanoic Acid)
ContaminantOne of the most well-studied PFAS compounds. Historically used in Teflon manufacturing. Associated with kidney and testicular cancer, thyroid disease, and immune system impairment. EPA’s 2024 MCL is 4 ppt (parts per trillion). EWG’s health guideline is 0.5 ppt. Reverse osmosis and NSF P473-certified carbon effectively remove PFOA.
TN context: Detected above EWG guidelines in Milcrofton UD and Spring Hill WD (Maury/Williamson County border area). Not detected in Nashville MWS, Lebanon, Smyrna, La Vergne, or the majority of Middle Tennessee utilities as of 2024 reporting.
PFOS (Perfluorooctane Sulfonate)
ContaminantOne of the original and most studied PFAS compounds, historically used in Scotchgard fabric protector and firefighting foam (AFFF). Associated with thyroid disruption, immune system effects, and increased cancer risk. EPA’s 2024 MCL is 4 ppt. Largely phased out of U.S. manufacturing but persists in water systems near airports, military bases, and industrial sites using AFFF.
TN context: Clarksville, TN (Fort Campbell area) warrants ongoing PFOS monitoring given the proximity of a major military installation with historical AFFF use. Clarksville WD 2025 CCR should be reviewed for PFOS status.
Pressure Tank
Well WaterA tank in a well water system that stores pressurized water and maintains consistent pressure throughout the plumbing, preventing the pump from cycling on and off with every small demand. Contains a rubber bladder or diaphragm with an air charge. A failing pressure tank causes “short-cycling” — the pump turns on and off every few seconds — which burns out pump motors prematurely.
TN context: Check your pressure tank quarterly by running a faucet and listening for rapid pump cycling. A healthy tank allows you to run a full glass of water without the pump starting. Short-cycling is a $500–$1,500 repair that is entirely preventable with early detection.
ppb / ppm (Parts Per Billion / Million)
MeasurementUnits of concentration. ppm (parts per million) = mg/L for practical water quality purposes. ppb (parts per billion) = micrograms per liter (µg/L) = 1,000 times smaller than ppm. PFAS is now regulated at the ppt (parts per trillion) level — 1,000 times smaller than ppb. These differences matter enormously when comparing a utility report (which may list in mg/L) to an EWG guideline (which may list in ppb or ppt).
pH
MeasurementA scale from 0–14 measuring the acidity or alkalinity of water. pH 7.0 is neutral. Below 7.0 is acidic; above 7.0 is alkaline. Ideal drinking water pH is 6.5–8.5. Acidic water (below 6.5) corrodes copper pipes and lead solder, leaching metals into water. Acidic water also prevents iron filters from working correctly. Alkaline water (above 7.5) typically accompanies hard limestone water.
TN context: Testing pH is mandatory before installing any iron filter for Middle Tennessee well water. Dickson County and Cheatham County chert/shale geology frequently produces acidic groundwater (pH 5.5–6.5). An acid neutralizer must be installed first. Never buy an iron filter without a pH test result.
POE vs. POU (Point of Entry vs. Point of Use)
MeasurementPOE (Point of Entry) systems treat all water entering a home at the main supply line — covering every tap, shower, and appliance. POU (Point of Use) systems treat water at a single location such as an under-sink filter or countertop RO unit. POE is required for scale (hardness), chlorine reaching every shower, and iron staining everywhere. POU is sufficient for drinking and cooking water only.
TN context: For TTHMs (absorbed through skin and inhalation during showers), a POE whole-house carbon filter is more protective than a POU kitchen filter alone. For PFAS affecting only drinking water, a POU RO at the kitchen tap is typically sufficient.
Q
Quarterly Monitoring
MeasurementEPA requires most surface water utilities to test for TTHMs and HAA5s at each sampling location four times per year (once per quarter). The four quarterly results are averaged to calculate the LRAA. Monitoring frequency requirements vary by contaminant and system size — some contaminants are tested annually or less frequently.
R
Radium-226 & Radium-228
ContaminantNaturally occurring radioactive elements that dissolve from uranium- and thorium-bearing geological formations into groundwater. Long-term exposure increases cancer risk, particularly bone cancer. EPA MCL for combined radium is 5 pCi/L. EWG’s health guideline is 0.05 pCi/L — 100 times more conservative. Reverse osmosis and ion exchange (water softener) both reduce radium.
TN context: Hendersonville Water System detected radium-226 and radium-228 combined above EWG’s 0.05 pCi/L health guideline — a distinctive finding unique among the 17 Middle Tennessee utilities in our guide series. Reverse osmosis effectively reduces radium at the drinking tap.
Radon
ContaminantA naturally occurring radioactive gas produced by the decay of uranium in bedrock. Dissolves into groundwater and is released into indoor air when water is used for showering, dishwashing, or laundry. Long-term exposure is a leading cause of lung cancer. EPA action level for radon in water is 4,000 pCi/L. Aeration or granular activated carbon systems remove radon from water.
TN context: Relevant primarily for deep bedrock private wells in Middle Tennessee. Recommend a one-time baseline radon-in-water test for any well deeper than 200 feet. Combined radon-in-air mitigation may also be appropriate.
Regeneration (Softener)
FiltrationThe process by which a water softener’s exhausted resin bed is restored to full capacity. A brine (salt) solution is drawn through the resin, displacing the accumulated calcium and magnesium ions and replacing them with sodium ions. Regeneration typically takes 1–2 hours and uses several gallons of water. Modern softeners regenerate on demand (by volume) or on a timer schedule.
TN context: In high-hardness areas (Murfreesboro, Smyrna, La Vergne at 10–14 GPG), softeners regenerate more frequently than at Nashville’s 5.9 GPG, consuming more salt. Ensure your brine tank is at least one-third full at all times — running out of salt allows hard water to pass through unconditioned.
Reverse Osmosis (RO)
FiltrationA high-performance water purification process that forces water through a semi-permeable membrane at pressure, rejecting dissolved contaminants. Removes up to 95–99% of TDS including PFAS, nitrate, chromium-6, arsenic, fluoride, radium, lead, and nanoplastics. Standard RO systems produce 3–5 gallons of waste water per gallon of filtered water. NSF/ANSI 58 certifies RO system performance.
TN context: The most comprehensive point-of-use drinking water solution available. Essential for Spring Hill area PFOA concerns, agricultural-area nitrate risk, and anyone replacing bottled water. At approximately 4 cents per gallon cost, dramatically cheaper than bottled water over time.
Bottled vs. Filtered: The Cost Comparison →
S
Sediment Filter
FiltrationA basic filtration system that captures physical particles — dirt, sand, silt, rust, and suspended solids — using pleated, string-wound, or spun polypropylene cartridges. Available in 5, 10, 20, and 50 micron ratings. Protects downstream equipment (iron filters, softeners, RO membranes) from clogging. Does not address dissolved contaminants, iron, chemicals, or bacteria. Always the first stage in any treatment sequence.
TN context: Required as the first stage in every Middle Tennessee well water system. Spring and fall rains stir up silt in aquifers — especially in agricultural areas of Maury, Robertson, and Wilson Counties. A clogged pre-filter reduces house water pressure and shortens the life of everything downstream.
Secondary MCL (SMCL)
RegulatoryNon-enforceable guidelines for contaminants that affect water’s aesthetic qualities — taste, odor, color — rather than posing direct health risks. Key SMCLs: iron (0.3 mg/L), manganese (0.05 mg/L), hardness (general recommendation <120 mg/L / 7 GPG), TDS (500 mg/L), chloride (250 mg/L), sulfate (250 mg/L). Utilities are not required to comply but may voluntarily aim for these levels.
TN context: Iron staining begins at 0.3 ppm — the secondary MCL. Most Tennessee well owners with noticeable orange staining are well above this level. Secondary MCLs give context for when water quality crosses from “barely detectable” to “visibly problematic.”
Salt (Softener Salt / Brine)
FiltrationSodium chloride (NaCl) or potassium chloride (KCl) added to a water softener’s brine tank to regenerate the resin bed. Sodium chloride is more common and less expensive. Potassium chloride is used by households on low-sodium diets or where sodium discharge is a concern. Neither option makes the softened water taste salty at normal settings — sodium content in softened water increases modestly but is well below dietary concern levels for healthy adults.
TN context: High-hardness areas (Murfreesboro 10–14 GPG, Williamson County wells 15–20 GPG) use significantly more salt than Nashville (5.9 GPG). Budget $180–$350/year for salt at 12 GPG for a family of four.
Salt-Free Conditioner (TAC / SP3 / NAC)
FiltrationA water treatment device that converts dissolved calcium and magnesium into microscopic crystals (typically aragonite) that remain suspended in water and are less likely to adhere to surfaces. Does NOT remove hardness minerals. GPG readings are unchanged after treatment. Reduces scale adhesion but does not provide the skin, hair, laundry, or soap benefits of true softening. No salt, no electricity, no wastewater.
TN context: Appropriate as a scale-reduction supplement at Nashville (5.9 GPG) and Clarksville (5.67 GPG). Not an adequate substitute for a properly sized salt-based softener at Murfreesboro, Smyrna, or La Vergne (estimated 10–14 GPG). Always ask the vendor: “After installation, will my water test at a lower GPG reading?” For salt-free conditioners, the answer is no.
Strontium
ContaminantA naturally occurring metal found in geological formations that can dissolve into groundwater. Associated with bone effects at high concentrations. Removed by water softeners through ion exchange — the same process that removes calcium and magnesium hardness. EWG flags strontium as a concern in some groundwater systems.
TN context: A standard water softener removes strontium as part of its normal hardness removal process. Middle Tennessee homeowners with a properly functioning softener are protected from strontium as a byproduct of hardness treatment.
T
Tannins
ContaminantNatural organic compounds from decaying vegetation that produce a persistent yellow to light-brown tea-colored tint in well water. Unlike ferrous iron (which runs clear and turns orange), tannin water is consistently discolored at the tap. Common in shallow wells with organic-rich topsoil. Iron filters and carbon filters are ineffective for tannins — specialized anion exchange resin is required.
TN context: Found in Wilson County and Cheatham County shallow wells. If you’re treating for iron and the yellow tint persists, test for tannins specifically before investing in additional iron treatment equipment. Tannin treatment is specialized and separate from iron treatment.
TDEC (Tennessee Department of Environment and Conservation)
RegulatoryTennessee’s state environmental agency, which has primary enforcement authority for drinking water standards delegated from EPA under the Safe Drinking Water Act. TDEC’s Division of Water Resources oversees public water system compliance, well construction standards, and septic system permitting in Tennessee. TDEC certifies water testing laboratories in the state.
TN context: TDEC can direct Middle Tennessee homeowners to certified water testing labs, licensed water treatment contractors, and public water system compliance data. Visit tn.gov/environment for current regulatory information and lab certifications.
TDS (Total Dissolved Solids)
MeasurementThe total concentration of all dissolved substances in water, measured in mg/L or ppm. Includes minerals, salts, metals, and other dissolved compounds. EPA’s secondary MCL for TDS is 500 mg/L. High TDS typically indicates hard water, mineral content, or contamination. Reverse osmosis systems are rated by their TDS rejection percentage (typically 95–99%). A TDS meter provides a quick overview but cannot identify specific contaminants.
TN context: Middle Tennessee’s limestone geology means naturally higher TDS in both city water and well water. A TDS meter is a useful first indicator but cannot distinguish between beneficial minerals and harmful contaminants. Always follow up with a certified lab test.
TTHM (Total Trihalomethanes)
ContaminantA group of four chemical compounds (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) formed when chlorine reacts with naturally occurring organic matter in water. Regulated collectively as TTHMs. EPA MCL is 80 ppb (LRAA). EWG’s health guideline is 0.15 ppb — more than 500 times more conservative. Associated with cancer risk and adverse reproductive outcomes. The most commonly exceeded EWG guideline in Middle Tennessee.
TN context: Nolensville NCGUD: 77.53 ppb LRAA (just under EPA limit). Brentwood NCGUD: 77.53 ppb LRAA. Gallatin CSB: 73.55 ppb LRAA. All surface water utilities produce TTHMs. Whole-house activated or catalytic carbon is the primary treatment.
Treatment Sequence (Filter Order)
FiltrationThe order in which water passes through multiple treatment stages. Correct sequencing is as important as correct media selection. The standard sequence for well water: (1) Sediment pre-filter, (2) Acid neutralizer (if pH < 6.5), (3) AIO iron filter, (4) Water softener, (5) Carbon filter, (6) UV sterilization, (7) Optional RO at the tap. Wrong order — particularly softener before iron filter — destroys equipment.
TN context: The most expensive mistake Middle Tennessee well owners make is installing a softener before an AIO iron filter. Iron above 1 ppm fouls softener resin permanently within 2–3 years. Iron first, hardness second — always.
Well Water Treatment Sequences →
Turbidity (NTU)
ContaminantThe cloudiness or haziness of water caused by suspended particles. Measured in NTU (Nephelometric Turbidity Units). EPA MCL for finished municipal water is 1 NTU (with no more than 5% of samples exceeding 0.3 NTU). High turbidity can shield pathogens from disinfection and UV treatment. A sediment filter is the primary treatment. UV sterilization requires clear water to be effective.
TN context: Turbidity spikes in private wells after heavy rain events across Middle Tennessee — a sign of surface water infiltration. Sudden turbidity in a previously clear well is a trigger for immediate bacterial testing. A spin-down sediment filter should be checked and cleaned after any significant rain event.
U
UV Sterilization (Ultraviolet Disinfection)
FiltrationA chemical-free disinfection system that uses UV-C light (254 nm wavelength) to damage the DNA of bacteria, viruses, and cysts (Cryptosporidium, Giardia), preventing them from reproducing. Does not remove any chemical contaminants. Requires clear water — turbidity or iron in the water shields microorganisms from the UV dose. UV lamp must be replaced every 12 months regardless of appearance. Quartz sleeve must be cleaned quarterly to remove limestone scale.
TN context: Required for every private well in Middle Tennessee. Annual April bacterial testing provides a snapshot; UV provides continuous protection. The lamp may glow while delivering insufficient germicidal dose after 12 months — replace on schedule, not by appearance.
Utility District (UD)
RegulatoryA government-created entity formed to provide water (or other utility services) to a specific geographic area. Utility districts in Tennessee are independent governmental bodies, not part of city or county government. They operate under TDEC oversight, publish annual CCRs, and set their own rate structures. Many Middle Tennessee communities are served by utility districts rather than city water systems.
TN context: Examples in Middle Tennessee: CUD Rutherford (Murfreesboro area), NCGUD (Nolensville/Brentwood area), Milcrofton UD (Spring Hill), Gladeville UD (Mount Juliet), H.B.T.S. UD (Thompsons Station). Each is a separate EPA-regulated entity with its own CCR and water quality profile.
V
Vanadium
ContaminantA naturally occurring trace metal found in some groundwater formations. Long-term exposure at elevated levels is associated with kidney and liver effects. Not regulated by EPA with a specific MCL, but EWG tracks vanadium in utility water data. Reverse osmosis is the most effective reduction method.
Violation (Water Quality Violation)
RegulatoryOccurs when a public water system exceeds an EPA MCL, fails to complete required monitoring, or fails to notify customers of a violation within required timeframes. Health-based violations (exceeding an MCL) are the most serious. Monitoring violations indicate testing was skipped or delayed but don’t necessarily mean the water was unsafe. All violations must be disclosed in the annual CCR.
TN context: All major Middle Tennessee utilities covered in our 17 city guides reported zero health violations in 2025. Tennessee Water Authority notes each utility’s compliance record in the city guides alongside EWG data.
VOC (Volatile Organic Compound)
ContaminantA broad group of carbon-based chemicals that can evaporate from industrial, agricultural, or manufacturing activities and contaminate water. Includes benzene, toluene, xylene, and industrial solvents. Many VOCs are known or probable carcinogens. Activated carbon and catalytic carbon effectively reduce VOCs. NSF/ANSI 53 certification covers VOC reduction.
TN context: Industrial areas near Dickson, Clarksville, and along major transportation corridors may have elevated VOC risk in groundwater. A whole-house carbon filter is the primary protection for city water; an under-sink carbon or RO unit provides point-of-use protection for well water.
W
WQA Gold Seal (Water Quality Association)
RegulatoryAn independent certification from the Water Quality Association, the water treatment industry’s trade organization, verifying that products perform as claimed when tested to NSF/ANSI standards. Equivalent in rigor to NSF International testing. Some manufacturers pursue WQA Gold Seal instead of or in addition to NSF certification. Both are legitimate; NSF is more widely recognized by consumers and some regulatory specifications.
TN context: When comparing a WQA Gold Seal system to an NSF-certified system for the same contaminants, treat them as equivalent safety signals and focus instead on which specific contaminants each covers and what the Performance Data Sheet shows.
Filter Certifications Guide →
Well Water (Private Well)
Well WaterWater drawn from a subsurface aquifer through a drilled, bored, or dug well serving a single household or small group. Private wells serving fewer than 25 people are not regulated by EPA under the Safe Drinking Water Act — the well owner is entirely responsible for testing, treatment, and maintenance. Well water quality varies significantly by geology, depth, well construction age, and proximity to contamination sources.
TN context: Middle Tennessee has tens of thousands of private well users across Davidson, Williamson, Rutherford, Wilson, Robertson, Montgomery, Maury, Dickson, and Cheatham Counties. Annual April testing for bacteria, nitrate, iron, pH, and hardness is the minimum standard. A baseline test including arsenic is recommended for any deep bedrock well.
Middle Tennessee Well Water Guide →
Find out what’s in your specific water.
Every city guide uses the same terminology defined here, applied to verified CCR and EWG data for your utility.
Related guides