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Well water testing: Dependable laboratory results start in the field

Well water testing: Dependable laboratory results start in the field


Almost nothing is more precious and essential to our bodies than fresh drinking water.

Ensuring your well water is free from common bacteria is possible though laboratory testing. But dependable laboratory results start in the field.


Proper sampling techniques

One of the most common well contaminants is coliform bacteria. The coliform test is used to determine if water has been contaminated with feces or animal waste.

  • Coliform bacteria in well water pose urgent health risks, while chemical contaminants such as lead, copper or nitrates are health risks given prolonged exposures.

  • Coliform bacteria are found everywhere in our environment—in soil, on vegetation and in water. In fact, coliform is the most common microbe in natural waters. Found in feces of all warm-blooded animals, coliform in well water represent a real and urgent health risk for diseases like typhoid, dysentery, hepatitis A and cholera.

  • That makes sampling for coliform bacteria critical to obtaining accurate laboratory results of your well water

  • While sampling is simple, critical steps must be taken to avoid contamination and false positives

  • The total Coliform test is considered an indicator test and the presence indicates the possibility , but not certainty that diseases organisms may also be present in the water. Conversely, The absence of Coliform bacteria indicate there is a low probability of disease organisms being present in the water. The ability of this test to reliably predict the bacterial safety of the well water is critical since it is impractical to test for every type of disease-causing bacteria. Important exceptions to this are the group of protozoa such as Giardia and Cryptosproidium which can be present in the water with the absence of Coliform bacteria.


Sampling procedure

  1. Select the faucet or spigot to be sampled. (Avoid taking samples from leaky faucets where water runs from anywhere but the end of the faucet itself; faucets with back flow prevention devices, or hot water faucets)

  2. Remove all impediments to the faucet, such as purification devices, the aerator, or swivel connections. If there is a swivel connection that cannot be removed, avoid moving the faucet while bleaching and sampling.

  3. After removing all impediments, turn on the cold water and allow it to run for several minutes, long enough to purge the pipes of any “old” water, dirt and contaminants.

  4. Shut off the water and wipe the faucet outlet with a towel soaked with bleach. If contamination is suspected inside the faucet, spray the inside of the faucet with bleach and allow it to sit for a minute. Or disinfect inside the faucet by flaming (alcohol flame, Sterno, etc.) to evaporate any water present. This must be done very carefully to avoid damaging the faucet by using too much heat.

  5. Run the water for another several minutes to flush away the bleach, and to ensure the water is running from the source and not “old” water that has been sitting in the pipes.

  6. Care must be taken not to allow any contaminants to enter the bottle or the lid. Hold the lid in a vertical position and do not set it down. Never touch the inside of the bottle or the lid.

  7. When ready to take the sample, remove the seal from the top of the sample bottle, unscrew the lid and take a midstream sample by tilting the bottle and allowing the water to flow in. Fill the bottle to at least the 100mL line, but not completely full.

  8. Replace the lid and screw on tightly.

  9. Record all pertinent information on the Chain of Custody (COC) and sample label.

Place the bottle in a resealable bag. Place the bottle upright in a cooler of ice for transport.


Drinking water microbiology samples have a 30-hour holding time.

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