MCL stands for “maximum contaminant level,” and potential contaminants in water are assigned specific MCLs based on health and safety standards. As you may have guessed, the maximum contaminant level is the highest concentration of a particular contaminant that can be present in the water and still considered safe. In general, local authorities dictate MCLs and other safety standards related to water, and I will address the MCLs for a few primary contaminants in this area. While the MCLs in your area are likely similar or identical, you are encouraged to check with your local authority.
While public water supplies can occasionally have elevated levels of contaminants, the treatment facility analyzes and treats the water on an ongoing basis to ensure its safety and alerts homeowners to any issues and requirements for ensuring their water’s safety (such as boiling until the problem is resolved). Private wells, on the other hand, are the sole responsibility of the homeowner, so water analysis of wells is much more common than analysis of public water supplies when it comes to hiring a professional to collect in-home water samples.
Many homeowners aren’t aware that when they have their water tested the lab is only testing for contaminants ordered to be tested. As a result, you may be expecting the lab to test for every possible contaminant when, in fact, they may only be testing for bacteria. One homeowner we did an analysis for a while back was surprised to learn that her water contained a fairly high concentration of lead. She said that she’d had her water tested many times and it had never contained lead. In all probability, her water had likely never been tested for lead, but she simply wasn’t aware. This was verified by the fact that the item causing the lead problem had been in the house for quite some time.
Here at HPI, we test for the same contaminants with every water analysis. There are countless potential contaminants, but we test for those which the Pennsylvania Department of Environmental Protection (DEP) recommends because we want our clients to have a more full picture of their water’s quality. The contaminants we test for are bacteria (total coliform and E. coli), nitrates and nitrites, total dissolved solids, lead and the pH level.
The MCLs for each of these contaminants are as follows:
1. Bacteria: the total absence of total coliform and E. coli bacteria
2. Nitrates: 10 mg/L, Nitrites: 1 mg/L
3. Total Dissolved Solids: 500 mg/L
4. Lead: 0.015 mg/L
5. pH: must be between 6.5 and 8.5
Knowing these guidelines can be very helpful for determining your water’s overall quality and safety. Fortunately, there are several options for reducing or eliminating contaminants that exceed their MCL, but you have to have those specific contaminants tested to know their levels. If you own a private well, be sure to have it tested as often as recommended and to have multiple contaminants analyzed. Otherwise, you’ll likely assume your water is safe when it may actually contain elevated levels of certain contaminants that may pose a health hazard.
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