Lead in Drinking Water
Reprinted from the Pure Water Occasional’s November 2010 Issue.
Lead rarely occurs naturally in water. It gets there from mining operations or industrial processes, but most often it gets into drinking water through plumbing fixtures. Low pH can be a factor, because as the pH of water goes down, its ability to leach metals from pipes and fixtures goes up.
The risk of lead poisoning is highest in children and pregnant women. Children absorb 30-75 percent of the lead they ingest; while adults absorb only about 11 percent. Effects of lead poisoning include brain, kidney and red blood cell deterioration, coma and convulsions, and high blood pressure. Lead-damaged children experience slowed physical growth, hearing problems, and reduced intelligence.
Lead is powerful stuff. While most water contaminants are measured in parts per million, the EPA’s maximum contaminant figure for lead is only 15 parts per billion.
The best water treatment for lead is prevention in the form of replacing pipes with very old solder joints (the Safe Drinking Water Act imposed limits on lead in solder in 1986) and fixtures that can leach lead. Raising the pH of acidic water and amendments in total alkalinity levels can dramatically lower lead content as well. Phosphate-based corrosion inhibitors are also effective.
Actual lead removal is done fairly easily in drinking water with any good reverse osmosis unit. There are also cartridge filters with lead-removal properties built into them. KDF, special ion exchange resins, and activated alumina cartridges can all be used to reduce lead in drinking water.
For whole house lead treatment, a standard water softener can be an effective lead remover, but reduced flow rates must be observed. There are also carbon block cartridge style filters, but these restrict service flow considerably.
For more information about lead removal, see the Occasional’s Water Treatment Issues page on lead.