Oshkosh's water has very hard water (256 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.
Oshkosh Water Utility · Source: Lake Winnebago · Serves 66,816 residents
256
Hardness (PPM)
430
TDS (PPM)
1
Chlorine (mg/L)
5
PFAS (ppt)
3
Lead (ppb)
Hardness Scale: Where Oshkosh Falls
Soft 060120180250400+
Extremely hard waterPFAS above EPA limit
Oshkosh draws from Lake Winnebago at the Fox River outlet. Water is hard from central Wisconsin's glacial and limestone geology.
What Oshkosh's Water Means for Your Home
Oshkosh residents deal with some of the hardest municipal water in the country. At 256 PPM (15 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 256 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 Oshkosh homeowners discover this only after a water heater replacement or plumber visit.
PFAS contamination is a significant concern in Oshkosh. 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.
Contaminant
Detected
Health Guideline
Legal Limit
Status
Hardness (as CaCO₃)
256 PPM
< 60 PPM
No federal limit
⚠ Very Hard
Total Dissolved Solids
430 PPM
< 300 PPM
500 PPM
⚠ Elevated
PFAS (total)
5 ppt
4 ppt (EPA)
4 ppt (2024)
⚠ Above limit
Lead
3 ppb
0 ppb (no safe level)
15 ppb (action level)
✓ Low
Chlorine / Chloramine
1 mg/L
Taste threshold ~1.0
4.0 mg/L
✓ Normal
Nitrate
4 mg/L
5 mg/L
10 mg/L
✓ OK
Recommendations for Oshkosh Homes
🧂Water Softener
At 256 PPM (15 GPG), Oshkosh'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 Oshkosh household of 2 to 4 people, a 48,000-grain softener is the right starting size.
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.
Water quality can vary by neighborhood and season. The values above represent typical averages reported by Oshkosh Water Utility. 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.
Oshkosh'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 Oshkosh?
Yes. At 256 PPM (15 GPG), Oshkosh'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 Oshkosh home with 2 to 4 residents, a 48,000-grain system is the most common starting size.
What water filter is best for Oshkosh?
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 Oshkosh's water come from?
Oshkosh's drinking water is sourced from Lake Winnebago and treated by Oshkosh Water Utility. Oshkosh draws from Lake Winnebago at the Fox River outlet. Water is hard from central Wisconsin's glacial and limestone geology.
What is the hardness of Oshkosh water in grains per gallon?
Oshkosh's water hardness is 15 grains per gallon (GPG), which equals 256 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 Oshkosh water damage tankless water heaters?
Yes. Most tankless water heater manufacturers recommend water hardness below 7 to 11 GPG (120 to 188 PPM). At 15 GPG, Oshkosh'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 Oshkosh water safe for babies and infants?
Oshkosh'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 Oshkosh household per year?
At 256 PPM, hard water costs the average Oshkosh 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 Oshkosh 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 Oshkosh Water Utility Consumer Confidence Report. Hardness and contaminant levels represent typical average values and may vary by neighborhood and season. Last updated: 2026-02-12.