Well Water Filtration System Cost: $1,500 to $5,000 (2026)

National figures. The water test decides which line applies to you.

Is it urgent? Warning signs in your well water

If the rotten egg smell is in the air of the house, not just at the tap, it could be natural gas. National Grid says to leave right away and call 911 or the gas emergency number from a safe place outside; see gas smell in the house. Hydrogen sulfide gas can also build up in well pits, basements and well houses, and the Minnesota Department of Health says only trained well professionals should enter those spaces.

• Call now: a test showing E. coli, or nitrate above the EPA's 10 mg/L limit in a home with a baby under six months. Use bottled water and see the well water testing page for next steps.
• This week: a new rotten egg smell, orange or black staining, or a sudden change in taste or color.
• Can wait: hard water scale or a mild, long-standing taste. Test, then choose.

Test first: the water test picks the system

The Minnesota Department of Health says "No single treatment unit can remove all contaminants in water," so a system bought without a test is a guess. The EPA's WaterSense guide says well owners should test with a state-certified lab and use the results to decide whether treatment is needed. Penn State Extension adds: compare several dealers and get a written warranty. After installation, Minnesota says to test the treated water to be sure it works. Penn State's lab charges $60 for a standard package; see well water test costs.

Well water filtration system cost by type

HomeGuide's well water filtration guide (Apr 2026) and reverse osmosis guide (Jul 2025).

Which treatment fixes which problem

Minnesota Department of Health home water treatment fact sheet, except where noted.

The EPA's guide also lists what common units do not do: activated carbon does not remove nitrates, bacteria or dissolved minerals, and UV is not effective against chemicals such as heavy metals or organics.

Iron filter for well water

An iron filter for well water costs $1,000 to $3,500 in HomeGuide's guide, plus $200 to $600 for new media every 5 to 10 years. Penn State recommends iron at no more than 0.3 mg/L and manganese under 0.05 mg/L, and the Minnesota Department of Health says iron above 0.3 mg/L is usually considered objectionable.

• Softener: manufacturers say up to 10 mg/L of iron, but Minnesota says 2 to 5 mg/L is a more common limit. Penn State uses a softener when dissolved iron is below 5 mg/L.
• Polyphosphate: below 2 mg/L (Penn State).
• Oxidizing filter: combined iron and manganese of 3 to 10 mg/L (Penn State). Manganese greensand handles up to 10 to 15 mg/L in Minnesota's figures.
• Oxidation plus filtration: above 10 mg/L (Penn State).

Water softener for well water

A water softener costs $1,200 to $3,800 installed in HomeGuide's softener guide, with a $2,500 national average; its well filtration guide says $1,000 to $3,500. The Minnesota fact sheet calls softening the cheapest option for hardness. Softeners can take out some iron too, within the limits above.

Well water smells like rotten eggs: finding the source

The Minnesota Department of Health says hydrogen sulfide gas gives water a rotten egg taste or smell, and it can be natural in the ground water, made by sulfur bacteria, or made inside the water heater. Its source test:

• No smell from the cold tap: the water heater.
• Smell that fades after a few minutes of running: hydrogen sulfide in the ground water.
• Smell that stays: sulfur bacteria in the well or plumbing.

Minnesota says that in most cases the smell does not relate to the sanitary quality of the water, but to test for coliform and nitrate anyway. Penn State says most people notice hydrogen sulfide well below 0.5 mg/L and that it has no drinking water standard. HomeGuide prices sulfur treatment by air injection or carbon at $800 to $3,500.

The two extension services disagree on treatment limits. Minnesota puts activated carbon under 1 mg/L and oxidizing filtration such as manganese greensand up to about 6 mg/L. Penn State puts carbon below about 1.0 mg/L but greensand at only about 2 to 3 mg/L, aeration usually not above about 2 mg/L, and continuous chlorination most often above 6.0 mg/L.

They also disagree on the water heater anode rod. Minnesota says a magnesium anode can help turn sulfate into hydrogen sulfide, and Penn State's fix is to swap the magnesium rod for an aluminum one, warning that pulling the rod out could increase corrosion and may void the warranty. Virginia Cooperative Extension says the smell may come from a reaction with an aluminum anode and may be fixed by switching to magnesium. If the smell is only on the hot side, the water heater repair page covers anode replacement.

UV light for well water

A UV system costs $700 to $2,500 installed in HomeGuide's guide, with $50 to $150 a year for the lamp, which Penn State says is replaced about once a year. Penn State does not recommend UV where total coliform exceeds 1,000 colonies per 100 mL. UV disinfection is on Minnesota's list of treatments for bacteria.

Reverse osmosis for well water

An under-sink reverse osmosis unit costs $300 to $950 installed in HomeGuide's reverse osmosis guide, and $300 to $1,000 in its well filtration guide. Whole-house reverse osmosis is $4,800 to $8,000 in the first and $4,000 to $10,000 in the second. Reverse osmosis is on Minnesota's list for both arsenic and nitrate.

Arsenic in well water: limits and treatment cost

The EPA limit for arsenic is 0.010 mg/L, with a health goal of zero. HomeGuide prices arsenic media or reverse osmosis at $1,000 to $4,000 installed. The Minnesota Department of Health's 2017 estimates split it by where the unit goes:

Minnesota Department of Health, Water Treatment Units for Arsenic Reduction, 2017 cost estimates.

Nitrates in well water

The EPA limit for nitrate, as nitrogen, is 10 mg/L, and it warns that infants under six months who drink water above it could become seriously ill. Minnesota lists reverse osmosis, distillation and anion exchange with certified resins as the treatments. Do not boil water to treat nitrate; Minnesota says boiling concentrates it.

What is the best water filter for well water? Check the certification

The best filter for well water is the one certified for the contaminant your test found. The EPA's WaterSense guide lists the NSF/ANSI standards: 42 for aesthetic effects, 53 for health effects, 55 for UV, 58 for reverse osmosis, 62 for distillation and 44 for softeners, and says to confirm the performance data sheet names your contaminant. Minnesota says to choose a unit certified by NSF, UL or the Water Quality Association, and warns those groups do not certify units for every contaminant.

Upkeep counts too. Minnesota says unmaintained units can make water quality worse and can make you sick, and HomeGuide puts maintenance at $100 to $500 a year. In Minnesota, the installer should be a licensed plumber or licensed water conditioning contractor. Ask the company for its well contractor or pump installer license number and proof of insurance yourself.

Treatment is one part of a well system; the well pump repair hub lists the rest, and a dug or shallow well with repeated bad results may be cheaper to replace than to treat forever; see dug vs drilled well costs.

What to do about smelly, stained or unsafe well water

1. Run the smell test. Cold tap, hot tap, and after a few minutes of running. Write down which ones smell.
2. Get a lab test for coliform, nitrate, pH, TDS, iron, manganese, hardness and arsenic.
3. Match the result to the treatment with the table above before you talk to any dealer.
4. Ask for the certification (NSF/ANSI number) and the performance data sheet for each unit quoted.
5. Get two written quotes with a warranty, as Penn State suggests, and the yearly upkeep cost.
6. Retest after installation to confirm the system works.

More well pages: well pump replacement cost and well pressure tank. Calls go to an independent company that serves your area and takes this kind of job; hours vary. How calls work.