Legal limits do not equal optimal health. All contaminants on this page are within EPA legal limits. EWG exceedances reflect EWG’s more conservative health thresholds — not regulatory violations. Brentwood-area water is legally safe to drink.
Nolensville-College Grove UD: TTHMs at 77.53 ppb — highest of any utility in this guide series, near the EPA 80 ppb limit
The Nolensville/College Grove Utility District’s 2024 CCR confirms TTHMs at 77.53 ppb highest LRAA (range 37.20–81.80 ppb). The EPA limit is 80 ppb — meaning measured highs of 81.80 ppb exceeded it in at least one quarter. The official LRAA of 77.53 ppb remains within compliance and the utility reports no violation. But this is the highest TTHM reading of any utility in the Tennessee Water Authority guide series. NCGUD purchases from three sources — Metro Nashville, Town of Smyrna, and Mallory Valley UD — and TTHMs continue building as water travels through distribution pipes. A whole-house activated carbon filter is the single most impactful water quality investment for NCGUD customers.
2024 Official CCR Data — Nolensville/College Grove Utility District
NCGUD’s 2024 Water Quality Report is the most current verified data for Nolensville and College Grove residents. Water is purchased from Town of Smyrna, Metro Nashville, and Mallory Valley UD. TDEC SWAP: reasonably susceptible to potential contamination.
range 37.20–81.80 · EPA limit: 80 ppb
range 19.40–46.80 · EPA limit: 60 ppb
Lead 90th%: <2.00 ppb (2022)
10 contaminants detected
Sources: Town of Smyrna (surface water), Metro Nashville (surface water), Mallory Valley UD. TDEC SWAP: reasonably susceptible. TTHMs 2024: 77.53 ppb highest LRAA (range 37.20–81.80) — within compliance but the highest of any utility in this guide. HAA5: 36.55 ppb LRAA (19.40–46.80). Chlorine: 1.63 ppm avg (0.40–2.30). Nitrate (Metro): 0.180 ppm (0.126–0.249). Nitrate (Smyrna): 1.77 ppm. Nitrate (MVUD): 0.48 ppm. Fluoride (Metro): 0.68 ppm. Fluoride (Smyrna): 0.492 ppm avg. Fluoride (MVUD): 0.56 ppm. Sodium (Metro): 9.97 ppm (7.80–11.3). Sodium (Smyrna): 11.00 ppm. Sodium (MVUD): 10.10 ppm. Lead (2022): 90th% <2.00 ppb, 0/30 exceeded AL. Copper (2022): 90th% 0.104 ppm, 0/30 exceeded AL. Turbidity: Metro 99.5%, Smyrna 100%, MVUD 100%. Zero violations 2024. Board meets 2nd Tuesday monthly at 9:00 AM at utility office.
TTHMs: 43.5 ppb highest LRAA (13.4–65.5) — within EPA 80 ppb. HAA5: 27.8 ppb (7.8–36.0). Nitrate: 0.362 ppm. Hardness: 100.5 mg/L avg = 5.88 GPG (“moderately hard”). Lead (2025): 0.8 ppb 90th%, 0/85 exceeded AL. Chlorine: 1.60 ppm avg. Zero violations 2025. Contact: 615-862-4494 · water.nashville.gov.
Your Four Brentwood-Area Utilities at a Glance
Brentwood and Williamson County are served by multiple utilities. Check your water bill to confirm — it matters because TTHM levels range from 43.5 ppb (Nashville MWS) to 77.53 ppb (NCGUD) depending on which system serves your address.
Nashville Metro Water Services
Brentwood: one zip code, four very different water profiles
Brentwood’s 37027 zip is served by multiple utilities. Nashville MWS covers northern Brentwood bordering Davidson County; Mallory Valley UD covers much of central Brentwood; Nolensville-College Grove UD serves the Nolensville corridor to the southeast. All four draw from Cumberland River surface water, yet TTHM levels range from 43.5 ppb (Nashville MWS) to 77.53 ppb (NCGUD) — nearly a 2x difference driven by how far water travels through distribution infrastructure after treatment.
Contaminants Exceeding EWG Health Guidelines
All contaminants below are within EPA legal limits. NCGUD 2024 CCR and Nashville MWS 2025 CCR are the most current verified data. Mallory Valley UD and Gateway Utility figures are from EWG’s database.
(13.4–65.5 range)
EWG 2013–2024 data
EWG 2018–2023 data
(37.20–81.80 range)
All Four Utilities — Side-by-Side Comparison
| Contaminant | EWG / EPA Limit | Nashville MWS 2025 CCR |
Mallory Valley UD TN0000428 |
Gateway Utility TN0008271 |
NCGUD 2024 CCR |
|---|---|---|---|---|---|
| TTHMs (LRAA) | 0.15 ppb / 80 ppb | 43.5 ppb (13.4–65.5) | Above EWG | Above EWG | 77.53 ppb (37.20–81.80) |
| HAA5 (LRAA) | 0.1 ppb / 60 ppb | 27.8 ppb (7.8–36.0) | Above EWG | Above EWG | 36.55 ppb (19.40–46.80) |
| Bromodichloromethane | 0.06 ppb | 1.60 ppb · 27x | 5.78 ppb · 96x | 8.70 ppb · 145x | 8.12 ppb · 135x (EWG hist.) |
| PFOA / PFOS | 0.09 ppt / 4 ppt | Above EWG (EWG data) | Above EWG (EWG data) | Not in EWG data | Not reported |
| Chromium-6 | 0.02 ppb | Above EWG | Above EWG | Above EWG | Not in CCR |
| Nitrate (highest) | 0.14 ppm / 10 ppm | 0.362 ppm · 2.6x (2025) | Above EWG | Above EWG | 1.77 ppm (Smyrna source) |
| Lead (most recent) | 0 / AL 15 ppb | 0.8 ppb · 0/85 (2025) | EWG data | EWG data | <2.00 ppb · 0/30 (2022) |
| Hardness (verified) | — | 100.5 mg/L = 5.88 GPG (2025) | Not specified | Not specified | Not in CCR |
| Violations 2024/25 | — | Zero (2025) | Not verified | Not verified | Zero (2024) |
| Above EWG / Total | — | 7 of 11 | 11 of 19 | 10 of 15 | 9 of 15 |
Protecting Children & Pregnant Women in Brentwood
Brentwood is Tennessee’s wealthiest city — yet the water supplying many of its homes carries some of the highest TTHM levels in Middle Tennessee. NCGUD’s 77.53 ppb is a meaningful concern for pregnant women and young children in Brentwood.
Disinfection byproducts have been linked in studies to pregnancy complications including low birth weight, preterm birth, and neural tube defects at sustained exposure. NCGUD’s 77.53 ppb LRAA (highs reaching 81.80 ppb) is the highest of any utility in this guide series. The first trimester is the highest-risk window. For NCGUD and Gateway Utility customers who are pregnant, a whole-house carbon filter plus under-sink RO is the most protective setup available.
Nashville MWS 2025: 0/85 exceeded lead AL (0.8 ppb 90th%). NCGUD 2022: 0/30 exceeded AL (<2.00 ppb 90th%). Excellent system-level results. However, lead comes from home plumbing — Brentwood’s 1970s–1980s housing stock predates 1986 lead-free plumbing requirements. Flush cold tap 30 seconds before use in older homes. Use NSF/ANSI 53 certified filter for drinking water in any pre-1986 home.
No Brentwood-area utility approaches the EPA 10 ppm acute nitrate limit. The Smyrna source in NCGUD’s blend reads 1.77 ppm — above EWG’s guideline but well within the EPA limit. For infants under 6 months, use RO-filtered water for all formula preparation. Never boil tap water for infant formula — boiling concentrates nitrate rather than removing it.
PFOA is detected above EWG guidelines in Mallory Valley UD (central Brentwood). Since NCGUD purchases from Mallory Valley UD, PFAS in the NCGUD supply chain is plausible. Studies link PFAS to immune suppression, thyroid disruption, and developmental effects in children exposed during pregnancy and early childhood. Reverse osmosis provides the most complete household PFAS removal.
Your Pets & Brentwood Water Quality
The same contaminants affect pets — at proportionally higher exposure per unit body weight. NCGUD’s 77.53 ppb TTHMs are the highest of any utility in this guide series and the most relevant concern for household pets in this area.
A 15-pound dog drinking the same TTHM-level water as a 160-pound adult receives roughly 10x the relative exposure per pound of body weight. At NCGUD’s 77.53 ppb average, that relative exposure is the highest of any utility in this guide. Long-term TTHM exposure has been associated with elevated bladder cancer risk in some dog breeds. Fill your pet’s bowl from your RO-filtered tap.
Rabbits, guinea pigs, hamsters, and birds have tiny body masses — their relative contaminant exposure is far higher than a human’s. At NCGUD’s elevated TTHM levels and Gateway Utility’s high bromodichloromethane, chronic lifetime exposure warrants real care. RO-filtered water is strongly recommended for all small caged animals and birds.
Chlorine in Brentwood tap water (NCGUD: 1.63 ppm; Nashville MWS: 1.60 ppm) is directly toxic to fish and aquarium invertebrates. Never add untreated tap water to a tank. Activated carbon removes free chlorine. RO is the gold standard for sensitive species, reef tanks, and shrimp. Never boil tap water for aquarium use.
Dogs and cats: RO-filtered tap water for their bowl. Whole-house carbon is a meaningful improvement. Small animals and birds: RO or filtered water strongly recommended. Fish: Always dechlorinate tap water before adding to tanks. Use RO for sensitive species. Never boil tap water for aquarium use.
What Hard Water Is Doing to Your Brentwood Home Every Day
The Cumberland River flows through Tennessee’s limestone geology, picking up calcium and magnesium that treatment does not remove. Brentwood’s new-construction premium homes with tankless water heaters are especially vulnerable to scale damage.
Calcium and magnesium ions disrupt the skin’s moisture barrier after showering — dryness, irritation, and increased eczema risk for children. Hard water deposits coat hair with minerals making it feel rough and dull. Color-treated hair fades faster. A softener or KDF showerhead filter addresses this directly.
White spots and cloudy film are calcium carbonate — limestone in liquid form. When hard Cumberland River water evaporates in your dishwasher, minerals bond to glassware. Dishwasher detergent needs 50–75% more product in hard water. A softener eliminates spotting entirely and extends appliance life.
Mineral deposits build up in fabric fibers — clothes feel stiff, whites yellow, colors fade, towels lose absorbency. Clothes washed in hard water wear out up to 15% faster. Brentwood’s luxury new construction often includes premium appliances whose warranties may be voided without treated water.
Scale reduces water heater efficiency 8% per GPG (U.S. Dept. of Energy). Nashville MWS confirms 5.88 GPG average with seasonal highs to 7.51 GPG. Brentwood’s abundant Navien and Rinnai tankless water heaters are especially sensitive — heat exchangers fail significantly faster on untreated hard water.
Cumberland River Limestone Hard Water in Brentwood
Nashville MWS’s 2025 CCR confirms hardness at 100.5 mg/L avg (5.88 GPG), ranging 88.5–128.4 mg/L (5.17–7.51 GPG). For Mallory Valley UD, Gateway Utility, and NCGUD customers, hardness data is not available in current CCRs, but the same Cumberland River limestone source geology applies throughout Williamson County. Private wells can be significantly harder.
Brentwood Hard Water Impact Calculator
Cumberland River Limestone Hard Water Impact Calculator
Default: Nashville MWS 2025 verified avg 5.88 GPG. Mallory Valley UD / NCGUD customers: estimated 7–9 GPG typical from same limestone source.
Soft 3.5 GPG
Slightly Hard 7–10 GPG
Hard 10.5 GPG
Extremely Hard
Eco120°F
Standard130°F140°F
Tankless
PPM / mg/L
Grains per gallon
0–3Mod. Hard
3–5Hard
7–10Ext. Hard
10.5+
Brentwood & Williamson County Area Water Guide
Which utility serves your address depends on your specific location. Check your water bill — it matters because TTHM levels range nearly 2x between utilities in this same county.
Find Your Area
Chlorine Residual in Brentwood Water
NCGUD and the three other Brentwood-area utilities all use chlorine as their primary disinfectant. While chlorine effectively kills bacteria and viruses, the residual that reaches your tap is worth knowing — especially because it directly drives the formation of the disinfection byproducts (TTHMs, HAAs, chloroform, bromodichloromethane) that are Brentwood’s biggest water quality concerns.
Brentwood tap water runs at pool-level chlorine concentration
NCGUD’s chlorine residual is approximately 1.63 ppm at the tap. For comparison, the EPA-recommended range for a swimming pool is 1.0–3.0 ppm — meaning your Brentwood tap water contains chlorine at roughly the same concentration as pool water. This is within legal limits and effective for disinfection, but it is the direct cause of the elevated TTHMs and haloacetic acids in Brentwood water. An NSF/ANSI 42-certified activated carbon filter removes chlorine taste and odor completely and reduces the formation of disinfection byproducts at the point of use.
Bottom line: You cannot taste or smell chlorine at 1.63 ppm the way you do in a pool because pool water is on your skin, not passing through your palate. But the chemistry is the same — and in Brentwood water it reacts with Cumberland River organic matter to produce TTHMs at 77.53 ppb and bromodichloromethane at 145x EWG guidelines. A whole-house activated carbon system is the most effective way to intercept chlorine before it reacts with your pipes and fixtures.
What chlorine at pool levels does to your body and home
Chlorine strips the skin’s natural oils and disrupts the moisture barrier. At 1.63 ppm — daily shower exposure — it causes dryness, itching, and irritation. People with eczema or sensitive skin often notice significant improvement after installing a whole-home carbon filtration system.
Chlorine oxidizes hair proteins, breaking down the outer cuticle layer. This causes dryness, frizz, brittleness, and color fade in dyed hair. At pool-range concentrations, daily washing strips the natural sebum that keeps hair supple. A shower-head carbon filter or whole-house system prevents this entirely.
Chlorine is an antimicrobial agent — that is exactly why utilities use it. Consumed daily in drinking water, it does not distinguish between harmful pathogens and beneficial gut microbiome bacteria. Emerging research links chronic chlorinated water consumption to microbiome disruption and digestive sensitivity. An under-sink carbon or RO filter removes chlorine from drinking water completely.
Chlorine bleaches and degrades fabric fibers over time, causing colors to fade faster, whites to yellow, and fabrics to wear thin sooner than they should. This is especially noticeable on dark clothing and athletic wear. Whole-house activated carbon filtration extends the life of clothes and towels significantly — a measurable return on investment over time.
The same pool-level chlorine that causes red, irritated eyes when swimming is present in your shower steam. Daily inhalation of chlorinated steam during showers exposes mucous membranes to chlorine gas byproducts. People with asthma or respiratory sensitivity often notice shower-steam irritation that disappears after installing a carbon shower filter.
Dogs and cats absorb chlorine through their skin and ingest it while drinking tap water. Many pet owners report improved coat condition after switching to filtered water. Chlorinated water also stresses chlorine-sensitive houseplants — fiddle leaf figs, ferns, and tropical plants in particular. Letting tap water sit overnight allows some chlorine to off-gas, but carbon filtration removes it completely and instantly.
The fix is simple and affordable. An NSF/ANSI 42-certified activated carbon filter — whether whole-house or under-sink — removes chlorine completely at the point of use. For Brentwood homes concerned about both chlorine and the disinfection byproducts it creates (TTHMs 77.53 ppb, BrCHM 145x EWG, TTHMs, HAAs), a whole-house carbon system addresses both problems in one installation. See the filter recommendations below for Brentwood-specific sizing and pricing.
Filter Recommendations for Brentwood Homes
Disinfection byproducts are the dominant concern across all four utilities. NCGUD’s 77.53 ppb makes whole-house carbon filtration the most urgent investment of any city in this guide. Mallory Valley UD’s PFOA detection adds RO as a priority for central Brentwood. Hard water is a real appliance risk especially for new construction.
The Brentwood Water Treatment Recommendation
Get a personalized recommendation for your Brentwood address.
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