Water Quality in Joliet, IL

Joliet's water has very hard water (279 PPM). A water softener is recommended to protect plumbing and appliances. Read below for a full breakdown.

City of Joliet · Source: Des Plaines River wells, Lake Michigan pipeline · Serves 150,362 residents

279
Hardness (PPM)
325
TDS (PPM)
1
Chlorine (mg/L)
4
PFAS (ppt)
3
Lead (ppb)
279 PPM 0 400 Extremely Hard
CONTAMINANT LEVELS Hardness 279 PPM TDS 325 PPM PFAS 4 ppt Lead 3 ppb Chlorine 1 mg/L Nitrate 3 mg/L

Hardness Scale: Where Joliet Falls

Soft 060120180250400+
Extremely hard water

Joliet is transitioning from deep wells (extremely hard) to Lake Michigan water. Current hardness depends on neighborhood source.

What Joliet's Water Means for Your Home

Joliet residents deal with some of the hardest municipal water in the country. At 279 PPM (16.3 grains per gallon), the water contains high concentrations of dissolved calcium and magnesium picked up from the regional geology as surface water is treated and distributed. This is not a safety issue. The minerals are safe to consume. But they create real, measurable costs for homeowners. Hard water at 279 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 Joliet homeowners discover this only after a water heater replacement or plumber visit.

Beyond hardness, Joliet's water quality is generally within EPA guidelines for regulated contaminants. Chlorine is present at 1 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.

ContaminantDetectedHealth GuidelineLegal LimitStatus
Hardness (as CaCO₃)279 PPM< 60 PPMNo federal limit⚠ Very Hard
Total Dissolved Solids325 PPM< 300 PPM500 PPM⚠ Elevated
PFAS (total)4 ppt4 ppt (EPA)4 ppt (2024)✓ OK
Lead3 ppb0 ppb (no safe level)15 ppb (action level)✓ Low
Chlorine / Chloramine1 mg/LTaste threshold ~1.04.0 mg/L✓ Normal
Nitrate3 mg/L5 mg/L10 mg/L✓ OK

Recommendations for Joliet Homes

🧂 Water Softener
At 279 PPM (16.3 GPG), Joliet's water is extremely 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 Joliet household of 2 to 4 people, a 48,000-grain softener is the right starting size.
Learn more about this solution →

About Joliet's Water Supply

Water Utility: City of Joliet

Water Source: Des Plaines River wells, Lake Michigan pipeline

Population Served: 150,362

Hardness: 279 PPM (16.3 grains per gallon)

Water quality can vary by neighborhood and season. The values above represent typical averages reported by City of Joliet. 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 Joliet to Other Illinois Cities

Chicago

140 PPM · Hard

Naperville

220 PPM · Very Hard

Rockford

185 PPM · Very Hard

Springfield

227 PPM · Very Hard

Peoria

231 PPM · Very Hard

Elgin

191 PPM · Very Hard

Frequently Asked Questions About Joliet Water

Is Joliet tap water safe to drink?
Joliet'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 Joliet?
Yes. At 279 PPM (16.3 GPG), Joliet's water is extremely 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 Joliet home with 2 to 4 residents, a 48,000-grain system is the most common starting size.
What water filter is best for Joliet?
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 Joliet's water come from?
Joliet's drinking water is sourced from Des Plaines River wells, Lake Michigan pipeline and treated by City of Joliet. Joliet is transitioning from deep wells (extremely hard) to Lake Michigan water. Current hardness depends on neighborhood source.
What is the hardness of Joliet water in grains per gallon?
Joliet's water hardness is 16.3 grains per gallon (GPG), which equals 279 parts per million (PPM). This is classified as extremely hard. Most water softener manufacturers recommend treatment above 7 GPG. To convert: 1 GPG = 17.1 PPM.
Does Joliet water damage tankless water heaters?
Yes. Most tankless water heater manufacturers recommend water hardness below 7 to 11 GPG (120 to 188 PPM). At 16.3 GPG, Joliet'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 Joliet water safe for babies and infants?
Joliet'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 Joliet household per year?
At 279 PPM, hard water costs the average Joliet 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 Joliet 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 Joliet Consumer Confidence Report. Hardness and contaminant levels represent typical average values and may vary by neighborhood and season. Last updated: 2026-02-12.