Retesting for Coliform after Treating My Well

Almost three weeks after chlorine shocking my well I tested my well for coliform bacteria and it was absent. That is a really good sign, but not a full bill of health-yet.

IRL it looks more like white wine than this

This past spring when I tested my well water I found coliform bacteria present. Coliform bacteria are commonly found in soil, on vegetation, and in surface water. They also live in the intestines of warm-blooded animals and humans. Some coliform bacteria strains can survive in soil and water for long periods of time. Coliform bacteria do not usually cause illness. However, because coliform bacteria can be associated with sewage or surface waters, the presence of coliform bacteria in drinking water indicates that the well water may not be sanitary, other disease-causing organisms (pathogens) may be present in the well and water system.

There are three different groups of coliform bacteria; total coliform, fecal coliform and Escherichia coli (E. coli) each has a different level of risk. Total coliform serves as a proxy for fecal coliform and E. coli bacteria. My well was found to be contaminated with coliform but not E. coli or fecal coliform, so I had a nuisance bacteria problem. In many instances total coliform contamination are introduced in the well or plumbing system through damaged parts of the system or during repairs and do not originate in the water supply.

This was the first time that a water test found coliform bacteria present in my well water. I had replaced my damaged well cap over the winter so it was likely that the coliform bacteria had entered the well during that time. Coliform bacteria do not occur naturally in most aquifers. However, fractured or creviced bedrock groundwater aquifers can have naturally occurring coliform bacteria.

In an existing well system that formerly was bacteria free and has only coliform bacteria look first for defects. These include: openings at the top of the well; damaged or improperly sealed well cap, old, rusty, or damaged well casing; unprotected suction line; buried wellhead; damaged grouting: or pooling of water near the well head after storms because the source of the coliform bacteria may be infiltration from the surface from rain or snow melt.

I carefully checked the well and water system for points of contamination and repacked the soil around the well pipe to make sure it flows away from the well as much as possible. My well cap was installed last winter, so the new cap was still in excellent condition, I made sure it was tight, sound and clean.

Though it is standard procedure to retest a well before treating it, I immediately treated the well and plumbing system with 100-150 ppm chlorine for 16 hours to disinfect system. The reason I went to immediately disinfecting my well is that treating a well with chlorine also cleans out the well and eliminates iron reducing bacteria that I have had problems with in the past. I had actually been thinking of treating my well with chlorine sometime this year anyway.

After almost three weeks (because I went to visit my family for a few days) I retested the water for coliform bacteria using a home test kit from Enviro TestKits. I still have half a dozen sealed DIY bacteria test kits (several were used for other people’s houses) so I plant to test my well after the next big rainstorm and in another month. If coliform bacteria remains “absent” I’m done. If not, then it is time to install a long term disinfection system. No fooling around, I am responsible for ensuring that my family has safe and clean drinking water.