Water Quality in Naperville, IL

Naperville's water has very hard water (220 PPM) and PFAS above EPA limits (5 ppt). A water softener is recommended to protect plumbing and appliances. An activated carbon filter can reduce PFAS levels. Read below for a full breakdown.

City of Naperville · Source: Deep groundwater wells · Serves 149,540 residents

220
Hardness (PPM)
330
TDS (PPM)
0.8
Chlorine (mg/L)
5
PFAS (ppt)
2
Lead (ppb)
220 PPM 0 400 Very Hard
CONTAMINANT LEVELS Hardness 220 PPM TDS 330 PPM PFAS 5 ppt Lead 2 ppb Chlorine 0.8 mg/L Nitrate 2 mg/L

Hardness Scale: Where Naperville Falls

Soft 060120180250400+
Very hard water

Naperville draws from deep limestone wells producing very hard water typical of the Chicago suburbs. Water softeners are standard.

What Naperville's Water Means for Your Home

Naperville residents deal with some of the hardest municipal water in the country. At 220 PPM (12.9 grains per gallon), the water contains high concentrations of dissolved calcium and magnesium picked up from underground limestone and mineral formations. This is not a safety issue. The minerals are safe to consume. But they create real, measurable costs for homeowners. Hard water at 220 PPM costs the average household $800 to $1,200 per year in hidden expenses, including higher energy bills from scale-insulated water heaters, increased soap and detergent usage, and premature appliance failure. Many Naperville homeowners discover this only after a water heater replacement or plumber visit.

PFAS contamination is a significant concern in Naperville. At 5 parts per trillion, levels exceed the EPA's 2024 maximum contaminant level of 4 ppt. PFAS are synthetic chemicals that do not break down in the environment or the human body, which is why they are called "forever chemicals." Long-term exposure has been associated with increased cancer risk, thyroid disruption, and immune system effects. A whole-house activated carbon filter or point-of-use reverse osmosis system can reduce PFAS to safe levels. Look for NSF P473 certification when comparing products.

ContaminantDetectedHealth GuidelineLegal LimitStatus
Hardness (as CaCO₃)220 PPM< 60 PPMNo federal limit⚠ Very Hard
Total Dissolved Solids330 PPM< 300 PPM500 PPM⚠ Elevated
PFAS (total)5 ppt4 ppt (EPA)4 ppt (2024)⚠ Above limit
Lead2 ppb0 ppb (no safe level)15 ppb (action level)✓ Low
Chlorine / Chloramine0.8 mg/LTaste threshold ~1.04.0 mg/L✓ Normal
Nitrate2 mg/L5 mg/L10 mg/L✓ OK

Recommendations for Naperville Homes

🧂 Water Softener
At 220 PPM (12.9 GPG), Naperville's water is very hard. Scale will accumulate in pipes, water heaters, and on fixtures. A salt-based ion exchange softener removes the calcium and magnesium causing the problem. For a typical Naperville household of 2 to 4 people, a 48,000-grain softener is the right starting size.
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🔬 Activated Carbon Filter for PFAS
PFAS detected at 5 ppt, above the EPA maximum contaminant level of 4 ppt. PFAS are linked to cancer, thyroid disease, and immune system effects with long-term exposure. A whole-house granular activated carbon (GAC) filter or a point-of-use reverse osmosis system can reduce PFAS. Look for NSF P473 certification, which specifically tests for PFAS removal.
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About Naperville's Water Supply

Water Utility: City of Naperville

Water Source: Deep groundwater wells

Population Served: 149,540

Hardness: 220 PPM (12.9 grains per gallon)

Water quality can vary by neighborhood and season. The values above represent typical averages reported by City of Naperville. 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.

Compare Naperville to Other Illinois Cities

Chicago

140 PPM · Hard

Rockford

185 PPM · Very Hard

Springfield

227 PPM · Very Hard

Peoria

231 PPM · Very Hard

Joliet

279 PPM · Extremely Hard

Elgin

191 PPM · Very Hard

Frequently Asked Questions About Naperville Water

Is Naperville tap water safe to drink?
Naperville's water meets EPA legal standards for drinking water safety. However, legal limits and health-optimal levels are different things. PFAS levels exceed the 2024 EPA health standard, which is a concern for long-term exposure. 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 Naperville?
Yes. At 220 PPM (12.9 GPG), Naperville's water is very hard. Without a softener, expect visible scale buildup on faucets and shower heads, reduced water heater efficiency (15 to 25 percent higher energy costs), spotted dishes and glassware, and soap that does not lather well. A salt-based water softener is the standard solution. For a typical Naperville home with 2 to 4 residents, a 48,000-grain system is the most common starting size.
What water filter is best for Naperville?
The best filter depends on which contaminants you want to address. For PFAS, look for a filter with NSF P473 certification. Granular activated carbon (GAC) and reverse osmosis systems are both effective. Standard carbon pitcher filters may not remove PFAS adequately. See our softener vs. filter guide to understand the difference between these categories.
Where does Naperville's water come from?
Naperville's drinking water is sourced from Deep groundwater wells and treated by City of Naperville. Naperville draws from deep limestone wells producing very hard water typical of the Chicago suburbs. Water softeners are standard.
What is the hardness of Naperville water in grains per gallon?
Naperville's water hardness is 12.9 grains per gallon (GPG), which equals 220 parts per million (PPM). This is classified as very hard. Most water softener manufacturers recommend treatment above 7 GPG. To convert: 1 GPG = 17.1 PPM.
Does Naperville water damage tankless water heaters?
Yes. Most tankless water heater manufacturers recommend water hardness below 7 to 11 GPG (120 to 188 PPM). At 12.9 GPG, Naperville'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 Naperville water safe for babies and infants?
Naperville's water meets all EPA safety standards and is generally considered safe for preparing infant formula. The hardness minerals (calcium and magnesium) are not harmful. If your home has older plumbing, running cold water for 30 seconds before use is a good precaution to flush any lead from pipes.
How much does hard water cost a Naperville household per year?
At 220 PPM, hard water costs the average Naperville 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 Naperville 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 Naperville Consumer Confidence Report. Hardness and contaminant levels represent typical average values and may vary by neighborhood and season. Last updated: 2026-02-12.