How to Properly Test Well Water for Bacterial Contamination

Bacteria contamination can indicate a serious problem with your well water system, so proper testing techniques are important to properly identify the problem. Here we’ll review the common causes of bacteria contamination and provide tips on how to get the most accurate results on your water test.

About Well Water Bacteria

There are many different causes of a bacterial contamination, from poor well construction to film inside your home’s pipes. When a test is done for bacterial contamination, the lab looks for total and fecal coliform bacteria. This includes E. coli, which grows in the intestinal track of animals and is found in sewage and animal feces. These bacteria die off within about 30 days after leaving the host. Therefore, if coliform bacteria are found in a water supply over a long period of time, it indicates continuous contamination.

Most coliform bacteria are not harmful to your health, although E. coli can cause severe illness in some, with symptoms similar to food poisoning. Their presence does indicate that other, more harmful bacteria are present and pose a health risk.


•    Poor well construction: This includes a buried well head, inadequate well cap or problems with the well casing. Poor well construction can lead to many problems with you well supply and if this is the cause, a professional well service should be consulted.

•    Recent well repairs or construction: Bacteria in the dirt surrounding the well pump or solids inside the plumbing can lead to bacterial contamination. A water system should be thoroughly flushed after a new water pump or plumbing is installed.

•    Problems with the aquifer or surrounding soil: Bacteria in water are typically filtered out naturally as they flow through the soil, but in some cases, the geology doesn’t provide an adequate filter. If you have a shallow well with poor surrounding soil, you’ll likely need a new well.

•    Contamination within your water system: Some water treatment systems, like activated carbon filters that attach to a faucet, can grow bacteria if not changed regularly. Bacteria can also form on the inside of pipes and tanks. Timing the bacteria test right is key to ruling out these causes.


When you test your home’s water for bacteria, it is important to avoid contact with anything else that could inject even a tiny amount of bacteria from another source. It’s also a good idea to test after a heavy rain when water from the soil is most likely to flow into your well water system.

Here’s how you do it:
•    Use a non-swivel, cold water faucet to take your sample. Remove all filters and aerators.
•    Wipe the faucet with a chlorine solution or run the water on full-blast for 5 minutes. Then slow water to a trickle.
•    Open sample bottle and hold the cap facing down. Don’t put the cap down on the counter or elsewhere.
•    Fill the bottle, leaving about 1 inch of space at the top. Put the cap on.
•    Turn off the water. 

Multiple results are the key to proper testing. It’s very unusual to get more than one positive test result from error, while problems with your water usually show up in all the samples. Just one sample cannot be considered sufficient evidence to determine the long-term consistency of the home’s water quality.

Samples can be tested through your state health department or Department of Environmental Services. If you have questions about the testing procedure, Skillings & Sons can also help and advise you on possible solutions if test results come back positive.

Want more in-depth information on disinfecting your home water supply? Contact the water well experts at Skillings & Sons.