Nashville, TN Water Quality 2026: Cumberland River Source, 4 GPG Hardness, and the PFAS Monitoring Data

Nashville's Metro Water Services draws from the Cumberland River and delivers tap water that clears all federal drinking water standards as of Q1 2026, per EPA SDWIS compliance records. Hardness sits at approximately 4 grains per gallon, making Nashville one of the softest major municipal supplies in the South. Under EPA's fifth Unregulated Contaminant Monitoring Rule, which ran from 2023 to 2025, Nashville recorded no detections of any of the 29 PFAS compounds monitored. Lead came in at 0.0008 mg/L at the 90th-percentile household tap versus the EPA's 0.015 mg/L action level. The main treatment-related finding comes from EWG's 2015 to 2023 testing analysis: chlorination byproducts, specifically bromodichloromethane at 1.60 parts per billion and chloroform at 4.36 parts per billion, are present within federal limits but above EWG health guidelines. An activated-carbon filter or reverse osmosis system at the tap reduces both compounds.

How this data was compiled

The numbers in this article come from publicly available government and nonprofit databases. Primary sources are the EPA's Safe Drinking Water Information System (SDWIS), the EPA's UCMR5 occurrence dataset accessed via ToxinScout.com, the Environmental Working Group's Tap Water Database (covering 2015 to 2023 testing data submitted by Tennessee to the EPA), and hardness and lead data from ClearWater which aggregates EPA SDWIS records. Nashville Metro Water Services' 2024 Consumer Confidence Report, published by the city at nashville.gov/departments/water/water-quality in May 2025, was used for source water and treatment context. No internal Aqua Otter data or proprietary records were used.

Nashville water quality at a glance

EWG data reflects testing years 2015 to 2023, as submitted by Tennessee TDEC to EPA. EWG health guidelines are more stringent than federal MCLs and are based on cancer risk models and California OEHHA public health goals, not enforceable regulatory limits. Sources: EPA UCMR5, EWG Tap Water Database (TN0000494), ClearWater.

Source and treatment: the Cumberland River

Nashville Metro Water Services operates two surface water treatment plants: the Omohundro Water Treatment Plant and the K.R. Harrington Water Treatment Plant, both drawing from the Cumberland River. The Cumberland runs through limestone plateau terrain in Middle Tennessee, but by the time it reaches Nashville it carries relatively low dissolved mineral content compared with deep Indiana aquifers. That geology is the primary reason Nashville comes in near 4 GPG when central Indiana cities like Indianapolis run 16 to 22 GPG and Carmel runs near 19 GPG. For a direct state-by-state comparison, see our Indiana and Michigan hardness guide.

MWS uses conventional surface water treatment: coagulation, flocculation, sedimentation, filtration, and chlorine disinfection. Fluoride is added at approximately 0.7 parts per million, consistent with the U.S. Public Health Service recommendation. Corrosion control treatment is applied to minimize leaching of lead and copper from distribution and household plumbing. The treatment process is the reason lead readings at the tap are well below the action level even in older Nashville neighborhoods.

PFAS: what the UCMR5 data actually shows

EPA UCMR5 required all large water systems (serving more than 10,000 people) to test for 29 PFAS compounds from 2023 through 2025. Nashville MWS serves 778,153 people and was required to participate. According to the EPA UCMR5 occurrence data reviewed by ToxinScout.com as of Q1 2026, Metro Water Services recorded no PFAS detections above the minimum reporting level across all tested compounds. Zero detections.

That puts Nashville in a different category from much of the state. According to Mapscaping.com's analysis of the EPA UCMR5 Tennessee dataset, published April 2026:

• 87 Tennessee utilities reported at least one PFAS detection above the minimum reporting level.
• 38 utilities exceeded the EPA's final 4 ppt MCL for PFOA or PFOS.
• Roughly 1,167,597 Tennessee residents are served by utilities above the MCL.
• Roughly 2,547,498 Tennessee residents are served by utilities with any PFAS detection above the minimum reporting level.

Nashville is not in either of those groups. The no-detection result is likely related to the Cumberland River's relative distance from major PFAS point sources: there are no large-scale AFFF-using military installations in Davidson County's immediate watershed, and industrial PFAS manufacturing in Middle Tennessee is limited compared with parts of the state with legacy chemical manufacturing corridors.

Metro Water Services also conducted voluntary PFAS sampling in 2019, before UCMR5 requirements were in place, according to the Tennessee Department of Environment and Conservation. MWS stated its goal was to go above and beyond federal requirements. That voluntary data predates UCMR5 but signals the utility's monitoring posture. The 2023 to 2025 federal results confirmed no detections.

For comparison with a nearby city where PFAS has been a more active concern, see our analysis of Ann Arbor's PFAS treatment on the Huron River and the broader Indiana PFAS UCMR5 breakdown.

Disinfection byproducts: where Nashville water does require attention

The area where public data does flag Nashville water is disinfection byproduct formation. When Metro Water Services applies chlorine to the Cumberland River water, it reacts with naturally occurring organic carbon from the river and produces trihalomethane (THM) compounds. The EPA regulates total THMs as a group under an 80 parts-per-billion MCL. Nashville meets that limit.

EWG's database, which reflects Tennessee TDEC laboratory data from 2015 to 2023, shows two TTHM sub-compounds detected at levels above EWG's own health guidelines (which are more stringent than federal MCLs and are based on California OEHHA cancer risk modeling):

Source: EWG Tap Water Database, Nashville Water Department #1 (TN0000494). Testing period 2015 to 2023, data submitted by Tennessee TDEC. EWG health guidelines are based on California OEHHA public health goals and reflect a one-in-a-million lifetime cancer risk level. They are not enforceable regulatory limits.

The national average for bromodichloromethane is 5.89 ppb and the Tennessee state average is 3.91 ppb, according to EWG. Nashville's 1.60 ppb is lower than both averages, so while it exceeds EWG's 0.06 ppb guideline, it sits in a better-than-average position relative to other U.S. surface water utilities using chlorine disinfection.

The same is true for chloroform. Nashville's 4.36 ppb sits well below the national average of 16.2 ppb and the Tennessee state average of 17.7 ppb. Better than average is still above EWG's 0.4 ppb guideline, however. EWG guidelines are not regulatory targets; they reflect a one-in-a-million lifetime cancer risk level derived from toxicological modeling. Whether to install treatment is a personal risk decision, not a compliance requirement. An under-sink reverse osmosis system in Nashville removes both compounds along with any other dissolved solids.

Lead: what the distribution system data shows

Lead in tap water in Nashville comes from the distribution system and household plumbing, not from the Cumberland River or the treatment plants. Metro Water Services applies corrosion control treatment to inhibit lead leaching from service lines and interior pipes. The 90th-percentile lead result at sampled household taps was 0.0008 mg/L, according to EPA SDWIS data retrieved via ClearWater. The EPA's Lead and Copper Rule action level is 0.015 mg/L (15 ppb). Nashville's 90th-percentile result is 0.0008 mg/L, roughly 19 times below that threshold.

The 90th-percentile approach means the EPA looks at the concentration at the 90th percentile of sampled homes and compares it to the action level. Nashville's result of 0.0008 mg/L is extremely low, suggesting that even in the homes most likely to show elevated lead (older plumbing, longer stagnation times), concentrations remain well below the action level. Homes built before 1986, when lead solder was banned in plumbing, carry higher theoretical risk. An NSF/ANSI 53-certified lead-reduction filter at the kitchen tap eliminates any remaining uncertainty for those households.

How Nashville compares to Lexington and other nearby cities Aqua Otter serves

Nashville's 4 GPG makes it one of the softest cities in the Aqua Otter service territory. For context:

• Lexington, KY: 7 GPG from the Kentucky River. Chloramine disinfection (less TTHM formation). Five PFAS compounds detected under UCMR5, all below MCL. See the Lexington water quality guide.
• Indianapolis, IN: 16 to 22 GPG from White River and reservoir sources. Chlorine disinfection. PFAS detected but below MCL. See Indianapolis tap water quality 2026.
• Grand Rapids, MI: Approximately 8 GPG from Lake Michigan after lime softening treatment. TTHMs present within federal limits. No major PFAS concern from the lake source. See Grand Rapids water and RO systems.
• Raleigh, NC: Also a surface water city. See the Raleigh water quality 2026 breakdown.

Nashville's soft water means a traditional ion-exchange water softener is usually not the right first choice. The bigger treatment questions for Nashville homeowners are disinfection byproducts and future PFAS insurance. Activated-carbon filtration handles the DBPs. A reverse osmosis system handles both categories and adds the PFAS margin, even though Nashville has no current detections.

What Nashville homeowners should actually treat

Given the data above, the treatment priority list for a typical Davidson County municipal water customer looks like this:

1. Disinfection byproducts (TTHMs, HAA5s): Present within legal limits but above EWG health guidelines. Whole-house activated-carbon block filtration removes chlorine and TTHMs at every fixture. An NSF/ANSI 42-certified carbon filter addresses taste, odor, and chlorine. An NSF/ANSI 58 reverse osmosis unit addresses TTHMs plus any future PFAS concern specifically at the kitchen tap.
2. Hardness (optional in most cases): At 4 GPG, Nashville water is borderline soft. Softening is typically unnecessary unless you have specific appliance or skin-sensitivity concerns. A no-salt conditioner is more appropriate than an ion-exchange softener at this hardness level, since traditional softeners add sodium to water that is already low in minerals.
3. Lead (precautionary for pre-1986 homes): Nashville's utility-wide lead data is excellent, but homes with original plumbing from before the 1986 lead solder ban carry elevated risk. An NSF/ANSI 53-certified pitcher or faucet filter specifically rated for lead reduction eliminates the exposure at the kitchen tap.

The free Aqua Otter water test gives you your specific numbers at your specific fixture, not the utility average. On-site testing catches localized pipe conditions, elevation-related stagnation, and variations that the utility's distribution monitoring may not reflect. Our Nashville-area scheduling page shows available appointments.

Frequently asked questions