Well Water vs City Water: Neither Is Automatically Safer

Neither well water nor city water is automatically safer. Each source sits under a different set of rules, and those rules decide who tests the water and who reports the results. City water comes from a public water system covered by the Safe Drinking Water Act (SDWA) and is reported on each year. A private well is not regulated by the federal government under that law, so the owner is responsible for testing it and for any treatment.

At The Indoor Report, we compile and explain published standards and agency guidance. We do not test water, and we own no instruments. This page reports what the published sources say and names the source for each figure. Those sources are the U.S. Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention (CDC), the U.S. Geological Survey (USGS), state health departments and university extension services.

Where two sources word the same rule differently, this page gives both wordings and names each source.

Who Is Responsible for the Water

The owner of a private well is responsible for delivering safe drinking water to the household. According to EPA, the quality and safety of private domestic well water are not regulated by the federal government under the SDWA, and generally not by most state governments.

City water comes from a public water system. EPA defines a public water system as one with at least 15 service connections, or one that serves an average of at least 25 people for at least 60 days a year, whether its owner is public or private. A community system serves the same people year-round.

CDC describes a private system as typically unregulated when it serves no more than 25 people for at least 60 days and has no more than 15 connections. The two sources word this threshold differently, so this page presents the line between regulated and unregulated as varying by source.

Most people are on public systems. CDC says 9 out of 10 people get tap water from a public water system. EPA says around 15 percent of the U.S. population, more than 43 million people in more than 23 million households, relies on a private well. USGS gives the same 15 percent and more than 43 million people, and it also reports estimates of about 40 million people from 2000 and 2010.

CDC says people not served by a public system most likely use a private groundwater well. It also states that tap water from private wells is not regulated, treated or monitored by officials.

For a city customer, the utility must meet EPA standards and must tell customers if its water does not. For a private well, the owner holds that responsibility.

Neither supply is automatically safer. City water is tested by the utility under EPA rules and reported to the customer. A private well is tested by its owner.

What Regulation and the Consumer Confidence Report Give City Water Customers

EPA sets legal limits on over 90 contaminants. It also sets the testing schedules and methods that water systems must follow, and states may set stricter standards.

Utilities must meet EPA standards and must tell customers if their water does not. The Consumer Confidence Report (CCR) is the yearly document that carries this information for community water systems.

Community water systems must send a CCR each year by July 1. The report gives the water source and a summary of contamination risk. It lists regulated contaminants found and, for any violation, the health effects and the actions taken. Where nitrate, arsenic or lead are a concern, it includes information on them.

Each CCR includes phone numbers, among them EPA's Safe Drinking Water Hotline at 1-800-426-4791. Customers can get the report from their local supplier or through EPA's CCR search tool.

EPA's CCR rule questions and answers say systems serving 10,000 or more people will get the report twice a year, on July 1 and on December 31 with a six-month update. Smaller systems get one a year, and these new requirements begin in 2027.

CDC advises public water customers to review the annual report. For help reading the figures, see how to read a water report.

The sources here describe no equivalent report for a private well. A private well's results come from the owner's own test.

What Well Owners Have to Test and When

EPA recommends that private well owners test every year for total coliform bacteria, nitrates, total dissolved solids (TDS) and pH. Test for other substances when they are suspected.

Test more often if small children, elderly adults, or someone who is pregnant or nursing lives in the home.

Test right away after local water problems, flooding, construction or industrial activity, repairs or replacement of well parts, or any change in odor, color or taste.

Use only laboratories certified for drinking water testing. If a contaminant exceeds standards, contact the public health department and retest, because you may need a new source or a new well.

CDC says private well owners should test at least once each year for harmful germs and chemicals. It also recommends a yearly well checkup for mechanical problems and cleanliness, even if an unused well may be used later.

For the test plan itself, see our well water testing page.

Groundwater is naturally filtered, which may remove some germs and chemicals, depending on depth and local geology. CDC lists private well pollution sources as failing septic systems, leaks from landfills and underground fuel tanks, fertilizers and pesticides, runoff from cities or industry, animal feedlot waste, and natural chemicals such as arsenic or radon.

A USGS study of about 2,100 domestic wells found that roughly one in five had at least one contaminant above a human-health benchmark. Most of those contaminants were inorganic chemicals, including metals, radionuclides and nitrate. Except for nitrate, USGS says these are mainly natural in origin.

The same study found pesticides and solvents in 60 percent of the wells sampled, but those exceeded benchmarks in less than 1 percent. About half the wells had at least one nuisance contaminant outside EPA's recommended range for taste or odor. Microbial contaminants turned up in about one-third of the roughly 400 wells tested for them.

Nitrate and Coliform Bacteria Have Set Limits and Test Steps

EPA sets the maximum contaminant level (MCL) for nitrate at 10 milligrams per liter (mg/L) as nitrogen, and the MCL for nitrite at 1 mg/L. MCLs are enforceable standards. The total coliform MCL allows no more than 5.0 percent of samples to test positive in a month, and it applies to public systems, not private wells.

Minnesota Department of Health (MDH) says nitrate cannot be tasted, smelled or seen. Bottle-fed babies under six months old are at highest risk of methemoglobinemia, also called blue baby syndrome. Above 10 mg/L, MDH says to use another source such as bottled water. Above 3 mg/L, it says additional testing is suggested, and it recommends testing yearly.

Boiling is not a fix for nitrate. MDH says boiled water is not safe because boiling may concentrate nitrate. Illinois Department of Public Health (IDPH) says boiling does not reduce nitrate either.

IDPH gives this conversion: 10 mg/L as N equals 45 mg/L as nitrate. Its limit is mandatory for public water supplies and is a guide for private wells. It lists fertilized farmland runoff, septic tanks and feedlots as sources.

Mississippi State University Extension says coliform bacteria are common and are not necessarily proof of waste contamination. After a positive result, collect another sample and test it for fecal coliform or Escherichia coli (E. coli). E. coli definitely indicates contamination from human or animal waste.

Until results are back, Mississippi State advises bottled water, or boiled water if bottled water is unavailable. Retest in six months to a year, and at least once a year. Shock chlorination comes after the source is fixed. For the lab side, see our coliform bacteria water test page, and for disinfection see well water shock chlorination.

Taste, Hardness, Iron and Sulfur Are Separate from Health Limits

EPA's secondary standards are non-enforceable guidelines. Iron is set at 0.3 mg/L, a level tied to rusty color, metallic taste and staining. Manganese is set at 0.05 mg/L. Chloride and sulfate are each set at 250 mg/L, a level tied to salty taste.

Total dissolved solids are set at 500 mg/L, and pH is set between 6.5 and 8.5.

USGS classes hardness, measured as calcium carbonate in mg/L, as soft at 0 to 60, moderately hard at 61 to 120, hard at 121 to 180, and very hard above 180. USGS treats hardness as a nuisance. Its listed effects are buildup in plumbing, fixtures and water heaters, and soap scum.

Iron bacteria and sulfur bacteria are a separate problem. University of Georgia Extension says iron bacteria cause swampy, oily, cucumber or musty tastes and odors, but not the rotten-egg smell. They leave yellow, orange, red or brown stains, make water rust-colored, and can clog well screens and pipes.

University of Georgia Extension says no drinking water standards exist for iron bacteria, which have no listed health implications. Standard coliform and E. coli tests do not detect them.

Sulfur bacteria produce hydrogen sulfide, the rotten-egg odor. That odor is strongest in the morning or after water has sat unused, and the gas is highly corrosive.

For iron or sulfur bacteria, University of Georgia Extension recommends shock chlorinating active wells one to two times a year.

For the iron side, see our iron filter for well water page. For the odor, see well water that smells like rotten eggs. Softening is a separate question, covered on our best water softener for well water page, and the sources on this page give no softener guidance.

Well Quantity and Pump Failures Are a Separate Risk

University of Minnesota Extension says drought and heat can cause overpumping and a cone of depression around the well. That cone usually resolves in a short time when water use drops. Shallow wells have problems first.

Warning signs listed by University of Minnesota Extension include a submersible pump that sounds like it is sucking air, sputtering taps, cloudy or dirty water, and sand in the toilet tank.

Pressure tanks and pumps can fail without warning. University of Minnesota Extension names the pressure tank, the pump and the electrical connection as the first parts to examine.

If a well runs dry, the options University of Minnesota Extension lists are a licensed driller lowering a submersible pump, a home storage tank, or a deeper well.

Test after a drought, or after air has entered the well, because air can release natural contaminants such as arsenic.

Penn State Extension says the most frequent cause of water shortage is a malfunctioning or worn-out submersible pump. Shallow hand-dug wells often dry up first in drought. Lowering the pump is usually a short-term fix, and deepening a well may not increase its yield. Penn State Extension points to a local driller or hydrogeologist for that decision.

The sources here do not give a figure for how long a well lasts or how long a well takes to run dry.

How Public Water and a Private Well Compare

The sources describe no yearly report for a home on a private well.

What to Do First on a Private Well

• Test every year for total coliform bacteria, nitrates, total dissolved solids and pH, using a laboratory certified for drinking water testing.
• Test again right away after flooding, nearby construction, repairs to well parts, or any change in odor, color or taste.
• If coliform bacteria are found, collect another sample and test it for fecal coliform or E. coli, and use bottled water until the results are back.
• If nitrate is above 10 mg/L, use another source such as bottled water, and do not rely on boiling.
• If a contaminant exceeds standards, contact the public health department, retest, and plan for a new source or well if needed.