Oregon State University Extension Service

How to test and treat my residential well water?

I am fairly new to using my well, and I had a few questions:

My well has a holding tank and the water tested positive for E. coli bacteria. I had a UV light installed and was wondering what else I should do to treat the water. Should I be using chemical treatments as well?

Do you have any recommendations for where to get my well water tested in the future and how to understand my results?

Thank you for your question! Be sure to check out OSU's Well Water Program webpage for additional information.

Treating your well water

Ultraviolet (UV) is the treatment that would kill the E. coli bacteria without additional chemical treatment. I always recommend UV installation at the end of the system, right before the water enters the home.

UV disinfection is very effective. If you are still wanting to shock the system, chlorinate the well and flush through the holding tank. One-time use of chlorine bleach will not damage the light.

If the UV is installed before the holding tank, you will want to shock just the water in the tank and flush at least 500 gallons of water out of the tank and through the rest of the system.

For more information about wells, check out the following resources:

Getting your well water tested

The following resources from the Oregon Health Authority (OHA) include a list of private labs that do well water testing in Oregon and other general information about testing:

Please note that there is a fee for testing.

The following tool from Colorado State University (CSU) can help you interpret your test results and get a general understanding of them. Unfortunately, this tool does not have Oregon as an option for which state you are from, so I use Utah and use this tool as a guide rather than a perfectly accurate interpretation.

Source URL: https://extension.oregonstate.edu/ask-expert/featured/how-test-treat-my-residential-well-water