Flushing Water Pipes Can Increase Lead Exposure

CC BY 2.0. Joe Shlabotnik

Do you run the tap for 30 seconds or a couple of minutes to ensure you are getting "clean water" instead of the water that has been standing around in the pipes?

A new study shows that flushing may make things worse. A team from the LSU Health New Orleans School of Public Health tested homes in New Orleans. They found that lead levels were at the highest concentration after typical flushing periods of 30 second to 2 minutes in over half of homes tested. Instead of reducing lead exposure as intended, the flushing maximized the risk.

The team collected samples after running the water for 30-45 seconds, 2.5-3 minutes and 5.5-6 minutes. They found no significant decrease in lead levels until after the 6 minute flushing interval. But even these reductions often were not substantial. And there is no guarantee that reductions achieved will last. LSU Health notes that "Some studies evaluating flushing at school taps suggest frequent flushes may be needed throughout the day, as waterborne lead can return to pre-flush levels within hours. Prolonged and repeated flushing may also not be practical, cost-effective, or sustainable over the long term, especially in cities with declining water resources and/or rising water rates.”

The lead author of the study, Adrienne Katner, pushes for a change to the public health messages, to communicate the "short-comings and practical limitations" of flushing water lines to reduce lead exposure.

Currently, the Centers for Disease Control and Prevention (CDC) recommends flushing for at least 5 minutes at a high-volume tap in the home (such as a shower) before an additional 2 minute flush at the tap from which the water for cooking or consumption will be drawn.

The US EPA recommends flushing the pipes for longer periods, see the italics (our emphasis), and defers some responsibility for the advice to the local water suppliers: "Let the water run to bring in fresh water that has not been standing in the pipes. Do this over a night or weekend. Flushing times can vary based on the plumbing configuration. It also depends on whether your facility has lead service lines. If you are unsure of the appropriate flushing time, contact your water utility."

But the only real solution to lead exposure in pipes is lead testing to determine the risk followed by replacement of pipes and plumbing, or at least the use of filters certified to reduce lead.

The best water filters are installed in the water line, but if all you can afford right now is a pitcher-style filter, you should note that most pitcher filters do not reduce lead exposure. The only pitcher-style filters certified by the National Sanitation Foundation (NSF) for lead removal are made by Zero Water - but take care to consult the NSF list because not all Zero Water filters are certified for lead. Be sure to follow the manufacturer's recommendations on replacement of filters to get the protection intended for yourself and your loved ones.

The full study is open source: Effectiveness of Prevailing Flush Guidelines to Prevent Exposure to Lead in Tap Water