Inside this issue of Water Currents: Rural Wells & Bacterial Contamination
Rural Wells and Bacterial Contamination
Your well water was tested by Public Health ON., and you were advised that your water is contaminated with bacteria. What do you do?
Today, more than ever, rural well owners are concerned about the water in their homes. The quality of drinking water can change from day to day, season to season. Even if your water is safe today, contaminants can infiltrate wells and aquifers and poor well integrity can lead to an increased risk of well water contamination. Well integrity should be assessed by a well driller.
Well water should be tested for bacteria once per year at a minimum, but more often is advisable due to seasonal changes and periods of high surface water runoff or even drought. It is very important that care be taken not to contaminate the Public Health sample bottles which could lead to false positive results. Follow their instructions carefully.
It is always best to try to determine the cause of contamination and correct it if possible.
Most Rural Wells:
- Drilled well can be deep or shallow with the well casing extending above ground
- Drilled well with the top of the well casing below grade in a well pit
- Dug well is often a wide hole dug in the ground, usually not more than 20 feet and encased with stone, metal or cylindrical cement tiles
Shallow Drilled wells, Drilled wells with well pits, and especially Dug wells are more susceptible to bacterial contamination than deep drilled wells. Deep drilled wells generally aren’t contaminated with bacteria.
Well pits – Many well pits will collect enough surface water to cover the top of the well casing. The well casing may only extend a foot or so above the bottom of the pit. The well casing should have what is referred to as a sanitary seal in the top of it. The sanitary seal is basically rubber compressed between steel plates to squeeze the rubber against the inside of the casing. It is designed to seal the well and prevent surface water contamination.
Shallow and Dug wells – are often contaminated with bacteria due to collection of water from an unconfined water table quite often within the first 20 feet and influenced by rainfall and drought. Water levels can vary with the season.
Disinfection
Wells are normally disinfected with chlorine. It can be done by the home owner or by a well driller. Home plumbing, including all outside lines should be disinfected at the same time. Outside lines could act as a dead end part of the home plumbing system and can harbor bacteria if not used very often. Dead end plumbing can then re-contaminate the rest of the plumbing with bacteria. Any existing water treatment equipment should be bypassed when chlorinating a well and not put back in service until the chlorine is gone.
If test results continue to be positive for bacteria, after well inspections, repairs and/or chlorination, an ultraviolet water sterilizer can be installed in the home for whole home water sterilization. It will be necessary to test the water to determine if the overall well water condition meets the requirements for a sterilizer. Also, sterilizers should be sized to the home owner’s flow rate and water usage.