Well Water Treatment Options: UV vs RO vs Softener vs Whole-House Filter

On this page

1. Rule #1: Test first, then treat
2. Whole-house vs single-tap
3. Which treatment for which problem
4. The main systems
5. Before you buy: a certification checklist
6. Sources

Rule #1: Test first, then treat

EPA advises that if a contaminant exceeds a health standard, you should contact your health department and have the well retested to confirm it before acting. Depending on the contaminant and the well’s condition, the answer might even be a new well or water source rather than a filter (EPA). Start here: How to Read Your Well Water Test Results (MCLs, ppm and ppb Explained)

Whole-house vs single-tap

• Point-of-entry (whole-house): treats all the water entering the home. Needed for problems that affect bathing, laundry or air, such as bacteria (in most cases), radon, hardness and iron.
• Point-of-use (one tap): treats drinking and cooking water, usually at the kitchen sink. Often enough for contaminants you only need to avoid swallowing, such as nitrate, arsenic, lead or PFAS. Minnesota’s health department explains the difference.

Which treatment for which problem

Each row is sourced in the linked article.

The main systems

UV disinfection

• What it does: inactivates microorganisms. Look for NSF/ANSI 55 Class A, which is designed to disinfect contaminated water of bacteria, viruses, Cryptosporidium and Giardia. Class B is only supplemental treatment for water already considered safe (ANSI).
• Requirements (per Penn State): incoming water must be completely clear, so a sediment filter usually goes first. The sleeve must be kept clean, and the bulb typically needs replacing about once a year. UV adds no disinfectant that persists in the plumbing, and it isn’t recommended where total coliform exceeds 1,000 per 100 mL or fecal coliform exceeds 100 per 100 mL.
• Scope: UV treats microorganisms. It isn’t among the treatments official sources list for chemical contaminants like nitrate, arsenic, lead or PFAS.
• Shop: SpringWell: UV systems → · US Water Systems: UV systems → · iSpring: UV systems →

Reverse osmosis (RO)

• What it does: a membrane holds back many dissolved contaminants. Minnesota’s health department says RO with pre-oxidation reduces “the widest array of contaminants,” including arsenic, lead, nitrate, PFAS and radium (MDH).
• Trade-offs: usually installed at a single tap. It sends a share of the water to the drain; EPA says about one gallon wasted per gallon treated for typical PFAS-reducing units (EPA). It needs pre-filters, and the membranes and cartridges must be replaced.
• Certification: NSF/ANSI 58, with a claim for your contaminant.
• Shop: SpringWell: reverse osmosis systems → · Aquasana: RO systems → · iSpring: RO systems → · APEC Water: RO systems → · Express Water: RO systems →

Water softener (ion exchange)

• What it does: removes hardness (calcium and magnesium) by swapping in sodium. Penn State says softeners can also remove some iron and small amounts of manganese, but generally only when pH is above 6.7, hardness is 3–20 grains per gallon, and dissolved iron is under 5 mg/L (Penn State).
• Nitrate is different: Penn State explains that nitrate ion-exchange units swap chloride for nitrate, which isn’t how a standard softener works (Penn State). See the nitrate article.
• Shop: SpringWell: water softeners → · US Water Systems: water softeners → · The Home Depot: water softeners →

Iron and manganese (oxidizing) filters

• What they do: oxidize dissolved iron and manganese into particles, then filter them out. EPA notes aeration and filtration both remove iron and manganese (EPA).
• Fit depends on iron and manganese levels, pH, and whether iron bacteria or hydrogen sulfide are present. Share your full lab report with the seller.
• Shop: SpringWell: whole-house well filters → · US Water Systems: iron filters →

Activated carbon (whole-house or under-sink)

• What it does: traps many chemicals. EPA lists carbon among filter types that can reduce PFAS when certified (EPA). For radon, EPA’s guide puts whole-house GAC at 85–95% reduction, but the carbon collects radioactivity (EPA radon guide).
• Certifications: NSF explains that NSF/ANSI 42 covers aesthetic claims (chlorine, taste and odor, iron, manganese and more), and NSF/ANSI 53 covers health-related claims such as lead, Cryptosporidium and VOCs. EPA adds PFAS reduction under 53 or 58. Check which claims a specific model holds.
• Shop: Aquasana: whole-house filters → · SpringWell: whole-house well filters →

Aeration (for radon)

EPA rates whole-house aeration at 95–99% radon reduction. It needs annual cleaning and venting to the outdoors (EPA radon guide). Work with your state radon office or a certified mitigation contractor.

Before you buy: a certification checklist

1. Confirm the claim, not just the logo. Look up the exact model in the certifier’s directory, e.g. NSF’s certified products listings. Minnesota also accepts certification by UL or the Water Quality Association for arsenic units (MDH).
2. Match the claim to your contaminant (e.g., “arsenic V,” “PFOA/PFOS,” “lead”).
3. Check pretreatment requirements against your test results.
4. Budget for maintenance: filters, membranes, UV bulbs and salt.
5. Retest the treated water after installation and periodically after that (MDH).

Not sure where to start? A water treatment professional can review your results. Minnesota points to the Water Quality Association’s provider search. Some state programs, and USDA Rural Development’s home repair loans and grants, may help eligible households with costs.