Guide to Navigating Water Test Results that Exceed the EPA's Maximum Contaminant Levels

What if my test results come back greater than the EPA’s maximum contaminant levels (MCL)?

The best way to protect against harmful contaminants in your water supply is to identify and eliminate the source of the problem. If that is not possible, then there are some temporary measures the Center for Disease Control (CDC) recommends to reduce your exposure to harmful contaminants.


1. Flush your tap water. Before using any water, run the kitchen tap or which ever you intend to use for drinking and cooking on COLD for 1–2 minutes.

2. Purchase a water filtration system. A water filtration system that’s been certified by an independent testing organization, such as The Public Health and Safety Organization (NSF), will reduce the contaminants in your tap water. For a list of certified filtration systems visit the NSF  or Water Quality Association’s database.

3. Buy bottled water. You can also reduce your exposure to contaminants by purchasing bottled water. Make sure to select a bottled water that’s been certified by an independent party.


When lead is present, here are some additional precautions to take into account:

The most important step when lead is detected is to determine if you can identify the source of the lead. Generally there are two sources where lead can enter your tap water - the service lines leading up to your home and your home’s plumbing. Depending on the age and location of your home lead could reside in both places.

In order to source the cause of the lead contamination, ask yourself these two questions:

  1. Does the service line pipe leading up to my property have lead? If you don’t know the answer:
    1. You should call a licensed plumber in your area to inspect your home’s plumbing.

The answers to these questions will help guide you toward which of the next two actions (A or B) you should consider to protect your household’s health.

A) If the service line pipe leading up to your home DOES NOT contain lead, the lead in your tap water may be coming from pipes inside your home.

Until you eliminate the source of the lead by replacing pipes, you should take the following steps any time you wish to use tap water for drinking or cooking, especially when the water has been off and sitting in the pipes for more than 6 hours:

  1. Before using any tap water for drinking or cooking, flush your water system by running the kitchen tap (or any other tap you take drinking or cooking water from) on COLD for 1–2 minutes;
B) If the service line connecting my home DOES contain lead, then the lead in the tap water may be coming from that pipe or connected pipes. Additional flushing is necessary.
  1. Before using any tap water for drinking or cooking, run high-volume taps (such as your shower) on COLD for 5 minutes or more;
  2. Then, run the kitchen tap on COLD for 1–2 additional minutes;
  3. Children and pregnant women are especially vulnerable to the effects of lead exposure. Therefore, for homes with children or pregnant women and with water lead levels exceeding EPA’s action level of .015 mg/L or 15 ppb, the CDC recommends using water from a filtration system or bottled water that has been certified by an independent testing organization to reduce or eliminate lead for cooking, drinking, and baby formula preparation. Because most bottled water does not contain fluoride, a fluoride supplement may be necessary.