Get the Lead Out
By Stephen E. Howe, PE
At the onset of the Safe Drinking Water Act in 1974, concern was raised over the presence of lead and copper in the drinking water. Recently, concern has again been raised over the amount of lead present in the water as a result of studies in Washington, DC. These studies indicated that in some homes with lead services, the level of lead increased from the first draw water sample to samples taken after one minute of flushing. It actually took five minutes of flushing to significantly reduce the lead levels. Information on the lead situation in Washington may be found at http://www.epa.gov/dclead/
The term plumber comes from the Latin root plumb, meaning working with lead. Lead water piping was used in Rome. Lead has also been used in modern times for water main lead and oakum joints. The oakum is held in place by the lead joint and swells up in the presence of water, keeping the majority of the water away from the lead. It has also been used in lead goosenecks to provide flexibility at connection of galvanized water services to the corporation valve and the water main. In some older cities, lead water services were also installed to customers.
The problem of lead in drinking water stems from corrosivity. Corrosive water leaches lead and copper from the piping. In New York State, there are some communities served by surface water supplies, which are relativity soft water. In addition, some ground water supplies may also be corrosive. The Langlier index has long been a measure of corrosivity. This measures the ability of water to absorb or deposit calcium. There are other indices for corrosivity as well. As the water becomes more corrosive on the index, its affinity for calcium reactivity increases. This affinity for minerals can also cause both lead and copper to be absorbed in the water. Temperature and the amount chlorine in the water affect corrosivity. At higher temperatures, the water is more corrosive. This can result in leaks in the hot copper piping, particularly in the hot water return piping. Lowering hot water temperatures may lead to other problems, such as legionella. Elevated chlorine levels such as in pool water, have caused so much corrosion problems in steel and copper piping that chlorinated polyvinyl chloride (CPVC) piping is permitted by State Education Department. Chlorine levels can also be affected by the closeness of a municipal chlorination station to the user or the need to chlorinate well water in certain instances.
The only way to find out if there is lead in the drinking water is to test the water itself. The EPA action level in drinking water for schools is 0.20 parts per billion (ppb) for lead and 1.3 parts per million (ppm) for copper. This is measured from the first 100-milliliter sample taken in the morning. The sample for residents is much larger, at 1000 milliliter. In one school, the entire copper piping system was replaced due to lead levels. A simple flushing program can be instituted as outlined by EPA. http://www.epa.gov/safewater/consumer/leadinschools.html. So the question remains, how do we get the lead out?
There are two approaches to this problem. The first is the chemical treatment of the drinking water by the municipality, or in the case of a well supply, by the school. A water treatment specialist is recommended to design a system for the addition of chemicals, which will modify the corrosivity by changing the acidity and alkalinity of the water. Of course, any water treatment must meet the requirements of the NYS Department of Health. For hot water corrosivity problems, the system can be protected with the addition of a chemical solution. This coats the interior of the copper pipe with silica, or phosphate, or other suitable chemicals. Again, a water treatment specialist is required for the design of the system.
The other methodology to eliminate lead is to remove the quantity of lead in the system itself. Ordinary red bronze, which has been used for years for fittings, valves, and faucets, contains up to 8% lead, which can leach into the drinking water. This can be decreased in a number of ways. Faucets are now produced by major manufacturers, which use brass mixtures that contain no lead or 2% or less lead. Wrought copper fittings can replace many bronze fittings. Valves can be obtained which are machined from yellow brass containing 2% or less lead, and even backflow preventers can be specified made from stainless steel. Hot water circulating pumps can also be purchased which are made from stainless steel. Electric water coolers and drinking fountains have long been available with no-lead lined interior waterways and optional lead filters. The systematic specification of low ((2%) or less) and no-lead materials as parts of the domestic water system can significantly decrease lead levels in the school drinking water.
In April 2004, the State Education Department and the Department of Health conducted a joint survey of lead in school drinking water through the Superintendents of Buildings and Grounds Association (SBGA). The purpose of the survey was to establish a snapshot of the status of lead in school drinking water across New York State. A total of 702 surveys were returned. Of the surveys returned, 528 indicated that the drinking water in the building had been tested for the presence of lead. A total of 120 noted that the sample results were greater than 20 ppb. Follow up actions included flushing, plumbing replacement, the use of bottled water, and water fountain replacement.
As a result of National Safe Drinking Water Act, the New York State Plumbing Code has long limited the amount of lead in red brass to 8% and has required less than 0.2% in solder to connect copper pipe. The National Safe Drinking Water Act Amendments has further limited the amount of lead in end use faucets, to NSF Standard 61 and has required less than 0.2% in solder to connect copper pipe. Projects have been submitted to SED specifying 50% lead and tin solder for joints in domestic water piping. Please note that this is not permissible.
Additional information on lead in school drinking water may be found at http://www.epa.gov/safewater/lead/schoolanddccs.htm
http://www.epa.gov/safewater/consumer/leadinschools.html
http://www.nsf.org/business/water_distribution/dwa_usepa.asp?program=WaterDistributionSys
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