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New Hampshire Department of Environmental Services

Frequently Asked Questions
  • What should I test my water for and how often?
    The list of contaminants below has been prepared by the Department of Environmental Services (NHDES) Water Supply Engineering Bureau after a review of the extensive records of NHDES’s public water supply program. This is not an exhaustive list, but provides a reasonable balance between the high cost of testing for all contaminants required by the Safe Drinking Water Act and those contaminants more commonly found in New Hampshire.
    • Recommended Testing for Bedrock Wells: bacteria, nitrate, nitrite, chloride, sodium, iron, manganese, pH, hardness, fluoride, arsenic, lead, copper, and radiologicals.
    • Recommended Testing for Dug Wells: bacteria, nitrate, nitrite, chloride, sodium, iron, manganese, pH, hardness, fluoride, lead and copper.
    • All of the parameters listed for a dug well are contained in NHDES’s "Standard Analysis" package.
    • Organic Chemistry Testing: Most contaminants in the organic group come from manmade sources. In general, testing for organic chemicals is not necessary unless an individual site review of the area near and uphill of your well identifies past or present land use that would make such contamination possible.
    Contact: Lou Barinelli, Technical Director (
    Publication: Suggested Water Quality Testing for Private Wells Adobe Acrobat Reader Symbol
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  • What is the difference between total coliform, E.coli and non-coliform bacteria?
    Total coliform bacteria are a group of easily cultured organisms used to indicate water quality. The US Environmental Protection Agency considers any total coliform to be unacceptable in drinking water. Total coliform bacteria consist of environmental and fecal types. Coliforms are easy to isolate, present in larger numbers and usually survive longer in an aquatic environment than viruses, parasites and more serious types of bacteria. Most of the total coliforms are not considered pathogens under normal conditions.
    E. coli is a species of coliform bacteria that is directly linked to fecal contamination by the wastes of warm-blooded animals, including humans. Some strains are pathogens in humans.
    Non-coliform bacteria are mainly environmental organisms and in large numbers can compete with total coliform and make it difficult for coliform(s) to be detected. High levels of non-coliform bacteria indicate a reduction in water quality.
    It is common for new wells or new plumbing to have high levels of bacteria resulting from the drilling and plumbing processes. If bacteria are present in a well, it may have construction problems allowing surface water and possibly animals to get into the well. It is sometimes necessary to disinfect the well more than once. Bacteria can also multiply in some treatment systems, especially iron filters.
    Contact: Mona Freese, Microbiology Supervisor (
    Publication: Interpreting The Presence Of Coliform Bacteria In Drinking Water Adobe Acrobat Reader Symbol
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  • How do I disinfect my well?
    Place the following amounts of disinfectant into the well:
    1. For Dug wells or drilled wells less than 200 feet deep, add one gallon of liquid bleach for every thousand gallons of water in your well. The number of gallons in your well can be found by multiplying the diameter of the well (in feet) by itself, then multiplying this result by 5.9. This number is then multiplied by the depth of the water in the well (in feet). The result is the volume of water in your well in gallons.
    2. For Drilled wells deeper than 200 feet, use calcium hypochlorite tablets (Chlorine pool tablets). Place the tablets in a heavy bag and break them into marble size pieces with a hammer (be careful, this material is hazardous). Pour into your well, 2 ounces of calcium hypochlorite for every 100 feet of well depth. Let it sit for several hours then continue with step two. This amount assumes your well casing is 6 inches (as most are) and that you are using 70 percent chlorine tablets (most range between 65 and 95 percent available chlorine).
    Once the disinfectant is in the well run each house faucet until you smell chlorine and then turn off faucet.
    Then run a garden hose from an outside faucet to the well. Turn the faucet on and let the chlorinated water run down the sides of the well. Recirculate the water back to the well for an hour or so.
    Now take the hose out of the well, reinstall the cover and let the whole system sit at least overnight.
    Over the next few days, flush the well by running an outside faucet. Do not run the well pump too long at any one time. Direct the flushing away from plants, since the strong chlorine solution will kill them. Do not drain chlorine into your septic system.
    Keep using the water until you can no longer smell any chlorine in the house (this may take several days). Then we recommend that you use the water for another week in order to allow any possible sources of contamination time to infect the well.
    Finally, have water retested for bacteria.
    Contact: Mona Freese, Microbiology Supervisor (
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  • What is the white flaky scale I see on my pots and /or faucets? Do I need a water softener or an oxidation filter?
    More than likely it is from calcium or magnesium commonly identified as hardness. The presence or absence of conventional hardness in drinking water is not known to pose a health risk to users. Hardness is normally considered an aesthetic water quality factor. The presence of some dissolved minerals in drinking water is typically what gives the water its characteristic and pleasant "taste". Iron and manganese are the "staining" elements and are generally aesthetically unpleasant. Your water’s pH, along with ratios of iron, manganese and hardness determine which treatment is warranted.
    Contact: Lou Barinelli, Technical Director (
    Publications: Hardness in Drinking Water Adobe Acrobat Reader Symbol
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  • How dangerous is arsenic in water?
    The US Environmental Protection Agency (EPA) has classified arsenic as a human carcinogen (cancer causing agent). Long-term exposure to arsenic has been linked to cancer, cardiovascular disease, immunological disorders, diabetes and other medical conditions. Specific health questions concerning arsenic should be directed to your personal physician or to the Department of Health and Human Services, Health Risk Assessment Bureau. EPA has recently revised the arsenic standard for public water systems from 0.050 mg/L to 0.010 mg/L.
    Contact: Lou Barinelli, Technical Director (
    Publication: Arsenic in Drinking Water Adobe Acrobat Reader Symbol
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  • My physician / dentist wants me to check the Fluoride in my water. Why?
    Fluoride occurs naturally in New Hampshire’s bedrock and it is frequently present in water samples taken from bedrock (drilled) wells. There are several regions in the state where fluoride concentrations are high.
    Fluoride in drinking water is beneficial at low concentrations, but can present health concerns at higher concentrations. It has also been shown to reduce tooth decay in children if they receive adequate levels. In order to determine if fluoride supplements are needed or to prescribe the proper dose, your dentist may ask you to have your water tested for fluoride.
    Contact: Lou Barinelli, Technical Director (
    Publication : Fluoride in Drinking Water Adobe Acrobat Reader Symbol
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  • Should I have my water tested for VOCs?
    The term "volatile organic chemicals" or "VOCs" refers to a group of chemicals (including MtBE) that are used as solvents and in many household products; they are also constituents in gasoline and fuel oil. These chemicals evaporate or volatilize when exposed to air. The most common sources of VOCs are products such as gasoline, fuel oils, degreasers, solvents, polishes, cosmetics and dry cleaning solutions. One should test for VOCs if your well is at risk from any of the sources mentioned above. The VOC test at most laboratories includes approximately 60 individual compounds.
    Contact: Lou Barinelli, Technical Director (
    Publication: Organics in Drinking Water Adobe Acrobat Reader Symbol
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  • What is MtBE and should I test for it?
    MtBE stands for methyl tertiary butyl ether. It is one of several oxygenates added to gasoline to enhance combustion, thus burning cleaner. It is released into the environment via transport accidents, leaking underground and aboveground storage tanks, leaking gasoline distribution pipes, watercraft and simple overfilling or sloppy practices.
    As an initial test, we recommend performing the full VOC analysis (above). If an original analysis has already determined that your well has been impacted by MtBE, the compound can be analysed independently so you will be able to monitor any changes.
    Contact: Lou Barinelli, Technical Director (
    Publication: MtBE in Drinking Water Adobe Acrobat Reader Symbol



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NH Department of Environmental Services | 29 Hazen Drive | PO Box 95 | Concord, NH 03302-0095
(603) 271-3503 | TDD Access: Relay NH 1-800-735-2964 | Hours: M-F, 8am-4pm

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