Division of Environmental and Community Health

Maine Center for Disease Control & Prevention

A Division of the Maine Department of Health and Human Services

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Water and Well Facts for Private Well Owners

Water and Well Facts for Private Well Owners

Page Index

Water Conservation

Dry Wells

Private Well Technical Assistance

Recommended Minimum Flow Rate for Single Family Homes

Well Disinfection

Coliform Bacteria

Trace Metals


Water Conservation

Much of the state of Maine has experienced drought conditions at some point in the past few years, with some areas seeing extreme drought. Trends indicate there will be more dry periods in the future. While the fall season typically brings rain to alleviate dry conditions, this is not guaranteed. Water conservation is one of the best ways to manage low water conditions and help your water supply last as long as possible. The following water conservation tips may help reduce water usage at your home.

Tips for Outside Water Conservation

  • Water garden plants only when necessary, either early in the day (before 9am) or late in the evening (after 5pm) to limit the amount of water lost to evaporation.
  • Allow lawn grass to grow a bit longer than usual. Less frequent mowing promotes soil moisture retention and helps vegetation develop a deeper root system.
  • Avoid watering lawns.
  • Avoid washing cars and other vehicles.
  • Limit the use of water for cleaning. Instead, use a broom on walkways, decks, and driveways.
  • Cover swimming pools when they are not in use to prevent evaporation.

Tips for Inside Water Conservation

  • Take shorter showers (approximately 5 minutes or less); avoid baths.
  • Turn off water while brushing your teeth or shaving.
  • Wash only full loads of laundry and dishes.
  • Collect and reuse clean household water. An example of this is to use water left over from cooking to water plants.
  • Fix any leaks you may find around the house. Toilets, for instance, can use up to 200 gallons of water per day.


Dry Wells

For homeowners who may be experiencing dry wells, there are several resources available that can assist with the costs of drilling a new well.

  • Single Family Housing Repair Loans & Grants (USDA)   This program offers loans to very low income homeowners to repair or improve their homes or grants to elderly very low-income homeowners to remove health and safety hazards. Applications are accepted year-round as long as funding is available. Applications will be processed in the order that they are received.
  • Emergency Community Water Assistance Grant (USDA)   This grant helps eligible communities prepare or recover from emergencies that threaten the availability of safe drinking water. Applications are accepted year-round and can be found online or through your local USDA Rural Development (RD) office.
  • Rural Decentralized Water Systems Grant (USDA)   This program helps qualified nonprofits and Native American tribes create a revolving loan fund to increase access to clean, reliable water and septic systems for households in eligible rural areas. The application period for this grant has passed, but prospective applicants may contact local RD offices for more information.
  •   Click here to locate the USDA Rural Development office closest to you.

  • Maine State Housing Authority Home Repair Program (MSHA)   This program provides assistance to low-income homeowners who cannot afford necessary home repairs, such as well repairs or replacements. For more information on the grants available and application process, applicants are encouraged to contact the Maine State Housing Authority directly.

The DWP strongly recommends against delivering water directly into a dry well. The water will likely quickly dissipate into the aquifer and not be available at the well. The delivered water may also contaminate your drinking water source.

Drought Informtation: A recent (2020) article from the Maine Emergency Management Agency (MEMA) includes resources for private well owners whose water supply is affected by drought. Consider completing the MEMA Dry Well Survey. Results from the survey help the Maine Drought Task Force determine how widespread water quantity issues are and what resources may be needed.

For assistance acquiring bottled water, please contact your local Emergency Manager (often your Town Fire Chief) or your County Emergency Management Agency office.


Private Well Technical Assistance

The Drinking Water Program can provide free help to private well owners who have questions about their wells, water sampling, and water treatment. (A "private well" being any well that is not regulated by the DWP as a Public Water System.)

This service offers property owners assistance with…

  • General well questions – Specialty Well applications, ideal well location, and potential threats to wells and water quality.
  • Drinking water and well drilling rules, best practices, and construction standards such as casing requirements and setbacks to septic systems.
  • Sampling – help with sample collection, explanation of test results, and follow-up testing. Guidance on laboratories is also available.
  • Water Quality Review – contaminants and the need for treatment.
  • Treatment – exposure risk assessment and treatment types to consider.
  • Disinfection advice on proper methods and products.
  • Potential conflicts between homeowners and drillers, abutting land owners, and local officials.

There is no charge for private well technical assistance. This is a free service of the Maine CDC Drinking Water Program.

To learn more, please contact Robert Jennings:  Email, or phone (207) 441-2568.


Recommended Minimum Flow Rate for Single Family Homes

These standards are based on a static water level of approximately 25 feet below ground surface. Every foot of a well's depth (6" diameter) holds approximately 1½ gallons of water.

Well Depth (FT) Recovery Rates (GPM)
75 5
110 4
160 3
250 2
320 1
420 1/2


Well Disinfection

  1. Remove the well cap. Using the dosage tables below as your guide, pour the appropriate amount of chlorine bleach (Clorox®, Dazzle®, or other EPA/NSF-approved bleach) into the well.
  2. Replace the well cap.
  3. Open all faucets, sill cocks, and similar outlets individually until you smell chlorine in each outlet.
  4. Allow the mixture to stand in the system overnight, then flush the chlorine mixture from the system using an outside faucet and garden hose.
    IMPORTANT: Do not flush the mixture into your septic system. A typical septic system cannot handle the large amount of water needed to flush the chlorine from the well. Also, since the chlorine will kill grass, be careful where you run the water outside.
  5. After disinfection, the water supply should be sampled and tested for coliform bacteria by an accredited laboratory. Sample kits for coliform bacteria are available from private and state labs. Check the yellow pages or click here for a list of certified labs. Sampling should be done only after the odor of chlorine disappears. It takes about 3 or 4 days of normal water usage before all of the chlorine smell disappears.

Learn more about Shock Chlorination.

Disinfection Dosages

Please Note:

  • For drilled wells, greater amounts of chlorine may be needed to disinfect the water depending on the degree of contamination.
  • In dug wells, depth refers to the approximate depth of water in the bottom of a well and not the total depth of the well.
  • For a surface spring, use 2 gallons.

Drilled Wells

Depth Dosage
50 feet 2 1/2 cups
100 feet 1 1/2 quarts
150 feet 2 quarts
200 feet 2 1/2 quarts
250 feet 3 quarts
300 feet 3 1/2 quarts

Dug Wells

Depth Dosage
5 feet 1/2 gallon
10 feet 1 gallon
15 feet 1 1/2 gallons
20 feet 2 gallons


Coliform Bacteria

Coliform bacteria make up a large group of bacteria that are found in soils, on plants, and in surface water. Certain coliform bacteria live in the intestines of humans and animals. Coliforms are used as an ‘indicator’ in drinking water. They are not harmful themselves, but if they are present, it means that disease-causing microorganisms such as bacteria, viruses, and parasites could have gotten into the water supply by the same route as the coliforms. It would be difficult, if not impossible, to test for every disease-causing microorganism, so we test for coliforms. If coliforms are present, there is a chance that the others are too.

Normally as water from the surface seeps downward through the soils, microorganisms are filtered out. When a test for coliforms is positive (meaning bacteria are present), it tells us that the microorganisms did not get filtered out and they made it into the drinking water supply. The water should be disinfected by applying chlorine bleach to the well water. After the system has been disinfected, the water needs to be retested for bacteria. You should wait at least 3 or 4 days after the chlorine odor has disappeared before resampling.

If a test for E. coli or fecal coliforms is positive, the water is not safe to drink! It should not be consumed unless it has been boiled for at least one minute at a rolling boil or disinfected by some other means. E. coli and fecal coliforms are indicators that the water has been contaminated with fecal wastes and it is very likely that it contains disease-causing bacteria, viruses, or parasites. These can cause intestinal upset as well as diseases such as dysentery, hepatitis, and giardiasis. IMPORTANT: If your water was positive for total coliforms and the water was not tested by the lab for E. coli or fecal coliforms, you cannot be sure they are not there and you should take the same precautions by boiling the water or disinfecting it as indicated above.

Most bacteria in wells or springs come from surface water contaminated by decayed animal waste or human activities. As surface water seeps downward through the soil towards the water table, these bacteria may be naturally removed by the soils. The extent of removal depends on the depth and character of the soil. In general, shallow wells and springs are more likely to contaminated than deep wells. Wells and springs must be properly located, constructed and maintained in order to prevent surface water from entering the well or spring. The presence of coliform bacteria and/or E. coli or fecal coliforms in wells or springs usually result from:

  • Well or spring covers that allow dust, rain, bird droppings, and other material to enter;
  • Wells or springs that are located in areas where surface water covers the well or spring during the wet periods of the year;
  • Defective steel well-casing seals;
  • Shallow wells or springs with rocked up sidewalls;
  • Recent changes or repairs to the well or spring, pumps, piping, etc; and,
  • Improper well location and/or construction.

If you have one or more of the problems described above, it should be immediately corrected. If the problem is not corrected, it may reoccur even after repeated disinfection.


Trace Metals

Trace metals may occur naturally in ground water in very small amounts and may include arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver, and zinc. In small amounts these are harmless (in some cases even beneficial to health). Amounts above the drinking water standards may have serious health effects.

  • Arsenic
    • Drinking Water Standards and Health Risks:
      The primary drinking water standard for arsenic is 0.01 milligrams per liter. Studies suggest that arsenic may be associated with several different forms of cancer, including bladder and skin cancers. Studies also indicate that arsenic in small amounts may be an essential element for normal human development.
    • Possible Source of Contamination:
      Arsenic contamination of water may be the result of dissolved minerals from local bedrock or sediments which contain arsenic, or it may be caused by leachate from solid waste landfills or from the use of pesticides.

  • Barium
    • Drinking Water Standards and Health Risks:
      The primary drinking water standard for barium is 2.0 milligrams per liter. Small doses are not harmful. Large amounts can cause increased blood pressure, nerve damage or cardiovascular disease.
    • Possible Source of Contamination:
      Barium pollution may come from natural sources or can enter water supplies through industrial waste discharges.

  • Cadmium
    • Drinking Water Standards and Health Risks:
      The primary drinking water standard for cadmium is 0.01 milligrams per liter. Cadmium in high concentrations can cause short-term intestinal illness. Since cadmium tends to accumulate in the body, long-term effects may occur, including intestinal, lung and kidney damage.
    • Possible Source of Contamination:
      Cadmium contamination may be caused by disposal of waste from photographic, metal plating or pesticide manufacturing industries. The most common source of contamination is from the corrosion by acidic water of galvanized pipes or soldered joints in copper pipes.

Updated 12/13/2023