Updated November 1, 2026

One river, two plants, 226,500 customers

All of Nashville's public water comes from the Cumberland River. Metro Water Services runs two treatment plants about a century apart in age. Together they deliver an average of 109 million gallons a day through more than 3,100 miles of main to over 226,500 customer accounts in Davidson County.

The plants

The system also has 54 pumping stations, 35 reservoirs and more than 22,000 fire hydrants. Intakes can draw from more than one depth in the river, which lowers the risk of pulling in a contaminated layer.

How river water gets treated

Water is screened for twigs and debris, then dosed with alum. The alum makes fine mud and algae clump together until the clumps settle (coagulation, flocculation and sedimentation). The clear water is filtered, disinfected with a small amount of bleach and fluoridated, as endorsed by the Metro Health Department. Filtered water stayed below 0.3 NTU turbidity in 99.9% of samples.

Rebuilding Omohundro

After a two-year pilot plant study that began in 2018, MWS started a 10-year Process Advancements Project. Its goals are to replace aging infrastructure, expand capacity, reduce flood risk and bring in new treatment technology. One piece of work so far is 4,670 feet of 72-inch and 84-inch tunnels for new and existing raw water intakes, pretreatment, the clearwell and a stream relocation. The flood goal is personal for Nashville, a city that knows how high the Cumberland can rise.

Limestone hardness

The Cumberland picks up calcium from limestone deposits across Tennessee and eastern Kentucky, and normal treatment leaves it in. 2025 tap water averaged 100.5 mg/L total hardness (88.5–128.4), of which 79.5 mg/L was calcium hardness. MWS calls that moderately hard. At about 5.9 gpg, you'll see spots on glassware, but many households manage without a softener. If you're thinking about one, the salt cost calculator shows the yearly expense.

Other 2025 figures

• Fluoride 0.67 ppm (0.56–0.75)
• Nitrate 0.362 ppm
• Sodium 12.2 ppm
• Total trihalomethanes 43.5 ppb (13.4–65.5, limit 80)
• Haloacetic acids 27.8 ppb (7.8–36.0, limit 60)
• Chlorine residual 1.60 ppm

River water carries more organic matter than groundwater, so trihalomethanes here run higher than in a well-fed city like Memphis, though they're still well within limits. A carbon filter reduces them and the chlorine taste. Our filter cost per gallon calculator compares cartridges.

Lead: corrosion control since 1987

MWS has run a corrosion control program since 1987, adding a blended phosphate that forms a protective film on pipe walls. In 2025 it sampled 85 sites, including lead service line locations. The lead 90th percentile was 0.8 ppb, no site was above the action level, and the highest result was 7.1 ppb. Copper's 90th percentile was 0.130 ppm. Water leaves the plants without lead; any lead at the tap comes from service lines or household plumbing.