Data sources: EPA, CDC, NGWA, USGS Last updated: March 2026

Why Well Water Is Different

Approximately 43 million Americans — about 13% of the U.S. population — rely on private wells for their drinking water (EPA Private Wells). Unlike public water systems, private wells are:

• Not regulated by the EPA or the Safe Drinking Water Act
• Not tested by any government agency (except sometimes at time of sale, depending on state law)
• Not treated — what comes out of the ground is what you drink, unless you install treatment
• The homeowner's full responsibility — you are your own water utility

This does not mean well water is unsafe. Many wells produce excellent water. But it means the safety of your water depends entirely on whether you test it and act on the results.

Testing Schedule

The EPA, CDC, and National Ground Water Association recommend:

Annual Testing (Every Year)

Test	Why	Cost
Total coliform bacteria	Indicates contamination pathway — bacteria from surface or animal sources may be entering the well	$20–$40
E. coli	Indicates fecal contamination (human or animal). A health emergency if detected	Included with coliform
Nitrates	Elevated by agriculture, septic systems, animal waste. Dangerous for infants at >10 mg/L	$15–$30
pH	Corrosive water (low pH) leaches metals from plumbing; alkaline water (high pH) causes scaling	$10–$20

Every 3–5 Years

Test	Why	Cost
Iron & manganese	Cause staining, taste issues, and plumbing buildup	$15–$25 each
Hardness	Affects appliances, soap efficiency, scaling	$15–$20
Sulfate	Above 250 mg/L causes laxative effect; hydrogen sulfide causes rotten egg smell	$15–$25
Total dissolved solids (TDS)	General indicator of mineral content	$15–$20
Lead	Test if plumbing predates 1986 or if water is acidic	$25–$50

Situational Testing

Situation	What to Test	Urgency
New home purchase	Full panel (everything above + arsenic, radon, PFAS)	Before closing
After flooding	Bacteria, nitrates, turbidity	Immediately — do not drink until tested
Near agriculture	Nitrates, pesticides, herbicides	Annually
Near industry or military base	PFAS, VOCs	Once (comprehensive)
Pregnant woman or infant in home	Nitrates, lead, bacteria	Immediately if not recently tested
Change in taste, color, or smell	Full panel	Within days
After well repair or pump work	Bacteria	1–2 weeks after work
Earthquake or nearby blasting	Bacteria, turbidity	Within a week

Where to Get Tested

Use a state-certified drinking water lab — not a home test kit. Find labs through:

• Your state drinking water program
• EPA lab locator
• Your county health department (many offer free or subsidized testing)

Common Well Water Contaminants

Bacteria (Total Coliform and E. coli)

Source: Surface water infiltration, damaged well casing, improper well cap, nearby septic systems, animal waste

Health risk: E. coli causes gastrointestinal illness (diarrhea, cramps, vomiting). In severe cases (E. coli O157:H7), it can cause kidney failure. Any detection means the well is compromised.

Treatment: Shock chlorination (immediate), UV disinfection (ongoing), well repair if contamination recurs

Nitrates

Source: Agricultural runoff (fertilizer), septic system leachate, animal feedlots

Health risk: Nitrates above 10 mg/L cause methemoglobinemia (blue baby syndrome) in infants — a potentially fatal condition where the blood cannot carry oxygen. Adults are less sensitive but chronic exposure may increase cancer risk.

Treatment: Reverse osmosis, ion exchange (anion exchange resin)

Note: Carbon filters do NOT remove nitrates. Filter guide

Arsenic

Source: Natural in certain geological formations (granite, volcanic ash deposits). Common in western U.S., New England, and parts of the Midwest.

Health risk: Bladder, lung, and skin cancer at chronic exposure. Skin lesions. Cardiovascular disease. MCL: 10 ppb.

Treatment: Reverse osmosis, specialized adsorptive media (iron-based), anion exchange. Arsenic contaminant page

Radon

Source: Uranium decay in granite and shale bedrock. Dissolves into groundwater.

Health risk: Radon in water releases into indoor air during showering and water use. Contributes to lung cancer risk. Radon guide

Treatment: Whole-house GAC (granular activated carbon) or aeration. Radon contaminant page

Iron and Manganese

Source: Natural — dissolved from soil and rock. Very common in well water.

Health risk: Minimal at typical levels, but iron above 0.3 mg/L and manganese above 0.05 mg/L cause:

• Orange/brown (iron) or black (manganese) staining of fixtures and laundry
• Metallic taste
• Pipe buildup reducing flow
• Recent research suggests chronic manganese exposure may affect neurological development in children

Treatment: Oxidation + filtration (iron/manganese filter), water softener (low levels), birm media, greensand. For technology comparison and sizing, see Best Iron Filters for Well Water. If you also have hard water, see Best Water Softeners. To test first, see Best Water Testing Kits.

PFAS

Source: Proximity to military bases (AFFF foam), industrial sites, agricultural land treated with biosolids, landfills.

Health risk: Cancer, thyroid disease, immune suppression, developmental effects. PFAS guide

Treatment: Reverse osmosis, GAC (for long-chain PFAS). Filter guide

Hydrogen Sulfide

Source: Sulfur-reducing bacteria in the well, or natural sulfate reduction in the aquifer.

Indicator: Rotten egg smell. Unmistakable.

Health risk: Low at typical levels, but corrodes plumbing and is extremely unpleasant.

Treatment: Aeration, chlorination, oxidizing filter (manganese dioxide), activated carbon

Interpreting Test Results

Since private wells have no regulatory standards, compare your results to EPA's public water standards as guidelines:

Parameter	EPA MCL/Guideline	Action If Exceeded
Total coliform	0 (no detection)	Shock chlorinate, re-test, consider UV
E. coli	0 (no detection)	STOP drinking immediately. Disinfect. Investigate source
Nitrates	10 mg/L	Do not give to infants. Install RO or ion exchange
Lead	15 ppb (action level)	Install NSF 53 or 58 filter. Check plumbing
Arsenic	10 ppb	Install RO. Test periodically (levels can change)
PFOA/PFOS	4 ppt	Install RO
Iron	0.3 mg/L (secondary)	Iron filter if staining/taste is an issue
Manganese	0.05 mg/L (secondary)	Filtration if staining occurs. Consider health-based limit of 0.3 mg/L
pH	6.5–8.5	Acid neutralizer (calcite) if below 6.5
TDS	500 mg/L (secondary)	RO if taste is affected

Use your ZIP code report to see what contaminants are common in your area — even though your well isn't in the EPA database, the geology and land use patterns apply.

Treatment Systems

Recommended Multi-Stage Well Water System

For well water with multiple concerns, a staged approach works best:

1. Sediment pre-filter (5 micron) — removes sand, rust, particles. Protects downstream equipment. $50–$100
2. Iron/manganese filter — if iron >0.3 mg/L or manganese >0.05 mg/L. Oxidizing media (birm, greensand, or catalytic carbon). $800–$2,000
3. Water softener — if hardness >7 gpg. Ion exchange, regenerates with salt. $800–$2,500
4. UV disinfection — kills bacteria and viruses. Essential for any well with a history of coliform. $300–$800
5. Under-sink RO — for drinking/cooking water. Removes lead, arsenic, nitrates, PFAS. $150–$500

Total estimated cost: $2,000–$6,000 for a comprehensive system. Many wells need only 2–3 of these stages.

Maintenance Schedule

Component	Maintenance	Frequency
Sediment filter	Replace cartridge	Every 3–6 months
Iron/manganese filter	Backwash (automatic)	Daily/weekly (automatic)
Water softener	Add salt	Monthly
UV lamp	Replace bulb	Annually
UV quartz sleeve	Clean	Every 6 months
RO membrane	Replace	Every 2–3 years
RO pre/post filters	Replace	Every 6–12 months

Well Maintenance

Annual Inspection Checklist

• Check the well cap — should be securely in place with no gaps for insects or surface water entry
• Inspect the visible casing — look for cracks, corrosion, or gaps at ground level
• Clear vegetation — maintain at least 2 feet of clearance around the wellhead
• Check for standing water — the area around the well should slope AWAY to prevent surface water infiltration
• Verify the pressure tank — check for waterlogging (the tank should feel half-air, half-water when tapped)
• Document the static water level — a declining level may indicate aquifer depletion or well problems

Warning Signs

Contact a well professional if you notice:

• Sudden change in water clarity, taste, or smell — possible contamination or well failure
• Air sputtering from faucets — water level may have dropped below the pump intake
• Pressure fluctuations — pump or pressure tank issues
• Pump cycling frequently — waterlogged pressure tank or leak in the system
• Visible sediment — well screen failure or aquifer changes
• Higher-than-usual electric bills — pump may be struggling

Well Records

Keep records of:

• Well log (from when the well was drilled) — depth, aquifer, yield, construction details
• All water test results with dates
• Well repairs and maintenance
• Treatment system installations and maintenance

Buying a Home With a Well

If you're purchasing a home with a private well:

1. Request the well log — depth, construction details, yield (gallons per minute). If unavailable, the state geological survey may have records

2. Get a comprehensive water test — bacteria, nitrates, lead, arsenic, pH, hardness, iron, manganese. Add PFAS if near a military base or industrial area. Add radon if in EPA Zone 1 or 2

3. Check the well age and condition — wells typically last 25–50 years. A well nearing end of life is a $5,000–$15,000 replacement cost

4. Test the yield — a flow test measures gallons per minute. Minimum recommended: 5 gpm for a single-family home. Below 3 gpm, you may need a storage tank or new well

5. Inspect for compliance — does the well meet current state construction standards? Is it properly sealed? Is the well cap intact? Is the wellhead at least 50 feet from septic systems?

6. Factor in treatment costs — if the water needs treatment, budget $1,000–$6,000 for equipment plus ongoing maintenance

7. Know the lender requirements — FHA and VA loans typically require a potability test (bacteria + nitrates at minimum) before closing

See also: Home inspection water checklist

Emergency Contamination

After Flooding

If your well has been submerged or impacted by floodwater:

1. Do not drink the water — assume it is contaminated
2. Do not turn on the pump until floodwaters recede below the wellhead
3. Visually inspect — check for damage to the well cap, casing, and electrical components
4. Shock chlorinate — follow your state's procedure for emergency well disinfection:
   • Calculate the well volume (depth × diameter)
   • Mix the appropriate amount of unscented household bleach
   • Pour into the wellhead
   • Run all faucets until you smell chlorine, then turn off
   • Wait 12–24 hours
   • Flush until chlorine smell is gone
5. Test for bacteria and nitrates 1–2 weeks after disinfection
6. If bacteria persist — the well casing may be damaged. Contact a licensed well professional

After Earthquake or Nearby Construction

Seismic activity and heavy construction can damage well casings or change groundwater flow paths:

1. Test for bacteria within one week
2. Monitor water clarity — turbidity may indicate disturbed sediments
3. Check for changes in yield or pressure
4. If changes persist, have the well professionally inspected

FAQ