Is Old Hickory, TN Tap Water Safe to Drink?
Yes, Old Hickory tap water is safe to drink. No contaminants exceed health guidelines. However, Old Hickory has hard water at 120 PPM, which will cause scale buildup in plumbing and appliances over time. A softener or conditioner is worth considering.
Hardness Scale: Where Old Hickory Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Old Hickory Compares
Old Hickory's water is close to the national average of 138 PPM, ranking #534 out of 1000 cities tracked. Within Tennessee, it ranks #8 of 20 cities (25% above the state average of 96 PPM). Among smaller cities, Old Hickory ranks #128 of 288 for hardness. At this hardness level, water heaters run an estimated 22% less efficiently due to scale insulation, and major water-using appliances typically last 2 years less than the national average lifespan.
What Old Hickory's Water Means for Your Home
Hardness: 120 PPM - Treatment Recommended
Old Hickory's water is hard at 120 PPM (7 GPG). That's enough to notice every day: gradual scale on fixtures, spots on dishes, soap that doesn't lather the way it should. That's 25% harder than the Tennessee average. Homeowners who install a water softener or salt-free conditioner notice the difference fast: better lathering, cleaner dishes, and appliances that last longer. That adds up. Hard water at 120 PPM increases household costs through scale-coated water heaters that use more energy, extra soap and detergent, and appliances that wear out faster. Most Old Hickory homeowners don't realize it until the plumber shows up.
Contaminants & Safety
Disinfection byproducts are the notable finding here. Old Hickory's water has TTHMs at 63.7 ppb and HAA5 at 18.4 ppb — both within legal limits, but the EWG health guidelines are far stricter. These byproducts form when chlorine reacts with organic matter during treatment. A whole-house activated carbon filter reduces both chlorine and its byproducts. Want the full picture? Request your utility's annual Consumer Confidence Report.
What's in the Treatment Process
Old Hickory's surface water supply requires heavy chlorination to stay safe — but that creates a tradeoff. The treatment process generates disinfection byproducts: TTHMs at 63.7 ppb (80% of the legal limit, but 425x the EWG guideline) and HAA5 at 18.4 ppb (31% of the legal limit, but 184x the EWG guideline). These are within legal limits, but the EWG sets much tighter thresholds based on cancer-risk research. A whole-house activated carbon filter reduces both chlorine and byproducts. All measurements are within federal legal limits. The EWG guidelines represent a more conservative, health-based standard.
How Hard Water Affects Your Home
At 120 PPM, untreated hard water has measurable effects on household costs and appliance life:
- Water heater inefficiency: Scale insulation forces the heater to work harder (DOE estimates up to 22% more energy for heavily scaled units)
- Soap and detergent: Hard water reduces lathering, requiring significantly more product
- Appliance replacement: Water heaters, dishwashers, and washing machines fail 2-4 years earlier due to scale buildup
- Plumbing maintenance: Scale buildup in pipes reduces flow and requires more frequent service
Note: Impact varies by household size, water usage, and local energy costs. A home water test provides the most accurate assessment for your specific situation.
| Contaminant | Detected | Health Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Hardness (as CaCO₃) | 120 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 200 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | Not tested | — | No total limit | N/A |
| Lead | 1 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ✓ Low |
| Chlorine / Chloramine | 1.4 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 1.12 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Our Top Picks for Old Hickory (120 PPM)
Hard water at 120 PPM causes scale buildup, increased energy use, and premature appliance failure. A softener protects your plumbing and appliances.
Quick Fix for Chlorine: Shower Filter
At 1.4 mg/L chlorine, many Old Hickory residents notice dry skin, brittle hair, and that "pool smell" in the shower. A shower filter installs in 5 minutes, no tools needed.
How to Test Your Water in Old Hickory
With 120 PPM hardness, a quick test strip confirms whether your specific tap matches Old Hickory's average before you invest in a softener. Hardness can vary within the same system.
Free option: Request Metro Nashville Water's annual Consumer Confidence Report for official city-level data.
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About Old Hickory's Water Supply
Water Utility: Metro Nashville Water
Water Source: Old Hickory Lake (Cumberland River) (Surface Water)
Population Served: 342
Hardness: 120 PPM (7 grains per gallon)
Old Hickory's drinking water comes from surface sources — Old Hickory Lake (Cumberland River). Surface water requires more extensive treatment than groundwater, including coagulation, filtration, and disinfection. This heavier chlorination is why disinfection byproducts tend to be higher in surface-supplied systems. Despite the treatment process, mineral hardness from the watershed carries through. The system serves 342 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request Metro Nashville Water's Consumer Confidence Report (CCR) or test your own tap.
ZIP Codes Covered by This Report
This water quality data applies to all areas served by Metro Nashville Water in Old Hickory, TN, including ZIP codes:
37076, 37087, 37088, 37115, 37121, 37122, 37138
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Water Softener Sizing for Old Hickory
At 120 PPM (7 GPG), here is how to size a softener for your Old Hickory home. Multiply hardness in GPG (7) by daily water usage (roughly 50 gallons per person). A family of four uses about 200 gallons/day: 7 GPG × 200 gal = 1400 grains/day. Over a 7-day regeneration cycle, that is 9,800 grains - a 32,000-grain softener is the right fit for most Old Hickory households.
Compare Old Hickory to Other Tennessee Cities
Frequently Asked Questions About Old Hickory Water
Is Old Hickory tap water safe to drink?
Where does Old Hickory's water come from?
Do I need a water softener in Old Hickory?
Does Old Hickory water damage tankless water heaters?
How much does hard water cost a Old Hickory household per year?
What is the hardness of Old Hickory water in grains per gallon?
What size water softener do I need for Old Hickory?
Salt-based softener or salt-free conditioner for Old Hickory?
Data sources: Lead and copper data from EPA Safe Drinking Water Act LCR reporting. Contaminant data from utility-reported testing results. PFAS data from EPA UCMR5 (2023–2025). Hardness from USGS and municipal reports. Data reflects system-level testing results and may not match your specific tap due to neighborhood plumbing, season, or recent utility changes. For your utility's latest results, request their Consumer Confidence Report (CCR). Our methodology. Last updated: 2026-02-24.
What Old Hickory Homeowners Actually Buy
Common purchases for homes with 120 PPM water.
Affiliate disclosure: we may earn a commission. Selection based on Old Hickory's water data.