Why should I test my Well water?
If you have a well, you should have it regularly tested to make sure the people living in your home are drinking clean water. Well water can be susceptible to many contaminants that can be harmful to your health. Even if your well has been tested in the past with great results, it's important to remember that things can change over time or even during different times of the year, so it is best to keep up with regular testing. See the Routine Testing tab below to learn how often to test your water.
If you are having a new well drilled or seeking a building or other well-related permit, you will need to have your water tested for multiple contaminants. This is a requirement before the Health Department can approve a permit.
Where can i have my well water tested?
Well owners can use the searchable map maintained by the Department of Ecology to find a lab that offers testing for drinking water. Contact the lab that you wish to use from the Department of Ecology's map for information on pricing and the correct way to collect and send in a water sample. The Snohomish County Health Department no longer provides water testing services.
Water testing for existing wells
To help make sure your drinking water is safe, regular water testing is recommended for all existing household water systems. Owners of private wells should test their drinking water based on the recommendations below:
Test for coliform bacteria at least once a year, or when...
- A household member has an unexplained illness
- You hear your neighbor's well is contaminated or they have a failing septic system
- You notice a change in your water's appearance, taste, or smell
- You replace or repair any part of your well system
- Your well has been flooded
Testing your water for coliform bacteria can tell you whether or not there is fecal pollution contaminating your well, either from a human source such as a septic system or an animal source such as livestock manure. Fecal coliform bacteria can cause illness in humans. Learn more about coliform bacteria testing from the Washington State Department of Health.
Test for nitrates at least once a year, or when...
- A household member is an infant under 12 months old
- A household member is pregnant, nursing, or trying to get pregnant
- You live in an area where fertilizers are, or have been, used near your well
Exposure to nitrates above the recommended level can cause illness and death in infants below the age of six months. Symptoms include shortness of breath and blue-baby syndrome. Nitrates can come from fertilizer runoff, leaking septic tanks/sewage, or erosion of natural deposits. Learn more about the effects of nitrates in drinking water from the Washington State Department of Health.
Test for arsenic twice a year, once in summer and once in winter, or if...
- You live in an area known to have naturally occurring arsenic in the groundwater (this is Snohomish County, we are in an area that is high in naturally occurring arsenic!)
- You know of neighbors who have high arsenic in their wells
Arsenic is naturally occurring in the Snohomish County region due to geological factors. Arsenic levels in groundwater and wells can vary over time, even from season to season. For example, a water sample taken in June might show different arsenic levels than a sample taken in December, and a sample taken in 2015 might show different levels than one taken just a year or two later. If you drink water containing arsenic in excess of the safe limits over many years, it can cause health problems. Learn more about the health effects of arsenic from the Washington State Department of Health.
A note about arsenic: When wells are permitted in Snohomish County, the water must be tested for arsenic among other contaminants. Well water that tests high must have an approved treatment system installed before the well can be approved, and an arsenic disclosure form will become part of the property's title record. However, because arsenic levels can vary, a well drilled years ago may not have had arsenic at the time, but it could now. This is another reason to test your well water regularly.
What about other contaminants?
If you have a concern about other contaminants, you can get your well water tested. The Washington State Department of Health has additional information on contaminants, and a helpful guide on what could be the cause if you notice something off with your well water.
You've tested your water, but what do the results mean?
The results of your test will show how much of each contaminant the lab tested for was present in the sample you provided. This shows a snapshot of your well water at the time the sample was taken. The Snohomish County Health Department has established primary drinking water requirements to help determine if your water supply is safe to drink. You can use the table below to see if your well water falls within safe limits for certain contaminants. These are also the contaminants that you are required to test for if you are seeking a permit or well site approval.
Maximum Contaminant Levels (MCLs): MCLs tells you the maximum amount of a contaminant in drinking water allowed. MCLs are set by the State Board of Health and EPA, and they are set to be as close as possible to the Maximum Contaminant Level Goals (MCLGs), which are levels at which no known or anticipated health effects would occur in a person. Snohomish County Health Department requires wells in our county to be at or below the MCLs listed below before they can be permitted.
Secondary Maximum Contaminant Levels (SMCLs): These levels set standards for contaminants that may make your water have an unpleasant taste, odor, or appearance. These contaminants are not considered to have a risk to human health at the secondary maximum contaminant level. You may want to test for these contaminants if you have reason to believe something is off with your well water.
Required for building & well permits?
|0 present using the presence/absence methods
|EPA Action Level
|No standard established
*In absence of an MCL established by the State Board of Health & EPA, SCHD applies the EPA “Action Level” of 0.015 mg/L.
**In absence of an MCL established by the State Board of Health & EPA, sodium testing is still required for permitting and an advisory will be sent if your levels exceed 20mg/L.
For more information on the contaminants above, visit the Environmental Protection Agency's recommended water quality criteria page. This will also tell you the MCLs for other contaminants.
what should i do if my water tests high for a contaminant?
If your well water tests below safe limits, great! Keep up with regular testing and maintain your well properly to make sure your water remains safe.
But what should you do if your water tests high for a contaminant? There are different steps to take depending on whether your well is already in use or still in the permitting and approval process.
if you have an existing well & are doing routine sampling:
If you are conducting routine sampling for your existing well and it tests high for a contaminant above Health Department standards, contact the Health Department by calling 425-339-5250 or emailing SHD-EHQ@snoco.org. You can also follow the recommendations below:
Remove or fix any possible sources of contamination. Are there fertilizers being used or stored nearby? Are there sources of human or animal waste that could be reaching your well? Is there damage to your well head? Look around for possible contamination sources and correct the issue. For instance, if your well tests high for nitrates and you've been applying fertilizer on your yard near your well, stop applying the fertilizer and then retest to see if the nitrate levels are lower.
Bacteriological contamination and disinfection. If your water sample shows bacteriological contamination (unsatisfactory levels of coliform bacteria, fecal coliform or E. coli) follow the CDC's recommendations for disinfecting your well.
if you're applying for any of the following:
- Individual Well
- Two-connection well
- Building permit served by an individual well,
...And the results from your water test show high levels of a contaminant above Health Department standards, your application will initially be denied and subject to further sampling and testing until it can show results within safe limits. The Health Department will advise you on next steps based on your situation. Sometimes it will just involve more testing, other times it may involve adding an approved filtration device to your water supply system. We will let you know what you need to do based on the results you submit.
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