Modesto's water has hard water (144 PPM) and elevated nitrates (6 mg/L). Read below for a full breakdown.
City of Modesto · Source: Tuolumne River, groundwater · Serves 218,464 residents
144
Hardness (PPM)
283
TDS (PPM)
0.7
Chlorine (mg/L)
4
PFAS (ppt)
2
Lead (ppb)
Hardness Scale: Where Modesto Falls
Soft 060120180250400+
Hard waterNitrates
Same Central Valley agricultural contamination as Fresno and Stockton.
What Modesto's Water Means for Your Home
Modesto's water is hard at 144 PPM. This level of hardness causes gradual scale accumulation on plumbing fixtures, inside water heaters, and on dishware. While not as aggressive as cities in the 200+ PPM range, homeowners who install a water softener or salt-free conditioner typically notice improved soap lathering, cleaner dishes, and longer appliance lifespans.
Beyond hardness, Modesto's water quality is generally within EPA guidelines for regulated contaminants. Chlorine is present at 0.7 mg/L as a disinfectant residual, which is normal for municipal water systems. If you notice a pool-like taste or experience dry skin, a whole-house carbon filter is the most common and affordable solution. For homeowners who want to understand the full picture, requesting your utility's annual Consumer Confidence Report provides neighborhood-level data.
Contaminant
Detected
Health Guideline
Legal Limit
Status
Hardness (as CaCO₃)
144 PPM
< 60 PPM
No federal limit
⚠ Hard
Total Dissolved Solids
283 PPM
< 300 PPM
500 PPM
✓ OK
PFAS (total)
4 ppt
4 ppt (EPA)
4 ppt (2024)
✓ OK
Lead
2 ppb
0 ppb (no safe level)
15 ppb (action level)
✓ Low
Chlorine / Chloramine
0.7 mg/L
Taste threshold ~1.0
4.0 mg/L
✓ Normal
Nitrate
6 mg/L
5 mg/L
10 mg/L
⚠ Elevated
Recommendations for Modesto Homes
💧Water Softener or Conditioner
At 144 PPM, Modesto's water is hard. You will see gradual scale buildup on fixtures and inside water heaters. A salt-based softener removes hardness completely, while a salt-free conditioner prevents scale without removing the minerals. Your choice depends on whether you want soft-feeling water or just scale prevention.
Nitrate measured at 6 mg/L, above the health guideline of 5 mg/L. Nitrate is especially dangerous for infants under 6 months (blue baby syndrome). A point-of-use reverse osmosis system under your kitchen sink is the most effective nitrate removal method for drinking and cooking water.
Water quality can vary by neighborhood and season. The values above represent typical averages reported by City of Modesto. To get exact numbers for your address, request a copy of the most recent Consumer Confidence Report (CCR) from your utility, or have your water independently tested.
Modesto's water meets EPA legal standards for drinking water safety. However, legal limits and health-optimal levels are different things. Review the contaminant table above for specific numbers and how they compare to both legal limits and health guidelines.
Do I need a water softener in Modesto?
It is worth considering. At 144 PPM, Modesto's water is hard. You will notice gradual scale buildup in pipes and on fixtures over time. A salt-based softener extends appliance life and improves soap efficiency. A salt-free conditioner is a lower-maintenance alternative if you primarily want to prevent scale.
What water filter is best for Modesto?
The best filter depends on which contaminants you want to address. See our softener vs. filter guide to understand the difference between these categories.
Where does Modesto's water come from?
Modesto's drinking water is sourced from Tuolumne River, groundwater and treated by City of Modesto. Same Central Valley agricultural contamination as Fresno and Stockton..
What is the hardness of Modesto water in grains per gallon?
Modesto's water hardness is 8.4 grains per gallon (GPG), which equals 144 parts per million (PPM). This is classified as hard. To convert: 1 GPG = 17.1 PPM.
Does Modesto water damage tankless water heaters?
Yes. Most tankless water heater manufacturers recommend water hardness below 7 to 11 GPG (120 to 188 PPM). At 8.4 GPG, Modesto's water exceeds this threshold. Scale buildup inside the heat exchanger reduces efficiency and can void the manufacturer's warranty. A water softener installed upstream of the tankless heater is the standard solution.
Is Modesto water safe for babies and infants?
Caution is warranted. Nitrate levels in Modesto are 6 mg/L, which is above the health guideline of 5 mg/L. Nitrate can cause methemoglobinemia (blue baby syndrome) in infants under 6 months. If you have an infant, use a reverse osmosis filter or bottled water for formula preparation until nitrate levels are confirmed below 5 mg/L.
How much does hard water cost a Modesto household per year?
At 144 PPM, hard water costs the average Modesto household an estimated $800 to $1,200 per year in hidden costs. This includes 15 to 25 percent higher water heating bills from scale insulation, 50 to 75 percent more soap and detergent usage, shorter appliance lifespans (water heaters, dishwashers, washing machines), and increased plumbing maintenance. A water softener typically costs $600 to $1,500 installed and $50 to $100 per year in salt, which means most Modesto households see a return on investment within 1 to 2 years.
Data sources. Water quality data compiled from EPA SDWIS, EWG Tap Water Database, USGS water hardness studies, and the City of Modesto Consumer Confidence Report. Hardness and contaminant levels represent typical average values and may vary by neighborhood and season. Last updated: 2026-02-12.