MSU Extension

As part of the response to the Flint, Michigan, water crisis, some homes have been provided with filters to help remove lead from water. How do these filters work? Are there limitations on what can be removed? Are there better alternatives to what is being provided? In this article, Michigan State University Extension addresses filters for drinking water, such as from a kitchen or bathroom faucet.

Some water filters use activated carbon to filter out impurities. The activated carbon works like a magnet, and lead and other impurities in the water get chemically “stuck” to the filter. Eventually, all the spaces on the carbon get filled up, and the filter must be replaced. How long a filter lasts will vary based on the type of filter you have, the amount of impurities in the water and how much water is moving through. Many filters have an indicator that specify when the filter needs to be changed. Check the filter’s instructions or product's owner's manual for this information.

Filters should be certified by an accredited organization such as the NSF International, a nationally recognized independent testing laboratory. An “NSF certification mark” will appear on all products they certify. Water filters should be used at points in the home where you will be consuming the water. If water in your home contains high levels of lead, this will also include water from the refrigerator or ice makers. You should use filtered water in ice cube trays or keep cold water from a filter tap in the refrigerator. When you are selecting a filter, consider how many gallons of water the filter can handle. Also consider the cost of the replacement cartridges as well as the initial filter.

Since there is only a limited amount of area within the filter for adsorbing lead and other materials, filters need to be regularly changed. Some devices can filter up to 100 gallons while others may filter only 40 gallons. It is important to read and follow the filter directions and make sure the filter is changed accordingly. However, if the contamination is high, the filter may need to be changed more often than the manufacturer’s recommendation. NSF International has recently compiled a list of all filters certified for lead reduction in drinking water. Filters listed are effective for up to 150 parts per billion lead. However, these filters have not been evaluated at higher lead concentrations.

Filters are rated to handle a particular level of contamination. If your water’s test results are beyond your filter’s capacity, you will need to consider another source of water. It is important to get your water tested to see what levels are in your home.

Improper treatment of Flint River water resulted in corrosive water running through service lines and household plumbing, which caused lead to leach from pipes and solder. The lead did not originate in the Flint River. The longer water stands in a pipe, the more chance there is for lead to be dissolved in it. When the water faucet is first turned on in the morning, or not used for some time, lead levels will be highest. The following steps, adapted from NSF International, may help reduce exposure to lead in the water supply:

• Running your tap for at least two minutes if the water has not been used for more than six hours is commonly recommended. Some health departments recommend running the water for up to five minutes prior to using it.
• Never use hot tap water for cooking, drinking or brushing your teeth since hot water dissolves more lead than cold water.
• Never drink water from any faucet other than the kitchen or bathroom tap; these are the only faucets in the home required to meet current lead content standards.

Other types of water treatment include distillation and reverse osmosis, which will be discussed in an upcoming article.

For more articles and resources about lead and lead exposure, see MSU Extension’s Fight Lead Exposure webpage.