LEAD IN DRINKING WATER
News of lead contaminated drinking water in Flint, Michigan in 2014 raised citizen interest and concern about lead in drinking water generally. While the contributing factors that resulted in the Flint water crisis are very specific to the water source and the age of water systems in that community, many people still have questions about their local water supplies. Even though Farmington is located within a geographic area that is well known for its lead mining, the deep aquifer ground source from which we obtain our water supply does not contain excessive or high amounts of elemental lead. Farmington does not use lead containing materials in any of its water system construction or renovation, and on the rare occasion that lead containing materials are discovered during routine maintenance, those materials are removed and replaced.
Lead contamination or exposure in the water supply at your home or place of business can result from other sources during the process of distributing the water from the deep water wells, through the municipal distribution system, and into the property owners plumbing system. In rare instances lead gets into water as a result of pesticides that were used decades ago or industrial activity that contaminated soil and groundwater. Lead is much more likely to enter water from household plumbing. For this reason, lead is a potential concern for all homes whether on a public (municipal) or private (individual well or spring) water supply. Depending on its other chemical characteristics, the water itself dissolves lead from leaded solder or lead pipes in plumbing systems in a process called “corrosion”.
Lead can also corrode from metal faucets and fixtures made from brass, which is an alloy of copper and zinc that often contains lead impurities, including chrome-plated brass fixtures. Brass fixtures can leach lead even in homes with plastic water lines. Solder is an alloy of tin with lead, antimony, or silver. Lead may also originate from the corrosion of brass fittings on certain types of submersible pumps used in groundwater wells through the mid 1990’s. Laws have restricted the amount of lead allowed in new pipes, fixtures, and solder but many homes contain older materials. Corrosive water also degrades copper plumbing, which may produce small leaks, blue-green stains, or metallic tastes, but these are not reliable indicators of the risk of lead in water.
The amount of lead corroded from metal plumbing generally increases as water corrosivity increases. Water corrosivity is controlled primarily by the water’s acidity and calcium carbonate content. In general, acidic water that has a pH less than 7 and that is low in calcium carbonate is more corrosive than water that has a pH higher than 7 and that is high in calcium carbonate. City of Farmington water was last monitored on July 21, 2015 for pH levels. They were found to range from 7.43 – 7.88. The secondary MCL for drinking water is 8.5.
In addition to acidity and calcium carbonate, many other factors can influence water’s corrosivity. Soft water (low in dissolved solids like calcium and magnesium) tends to be more corrosive than hard water (with high concentrations of calcium and magnesium) City of Farmington Water Hardness ranges from 11.6 to 26.3 grains /gallon so it is rather hard. Warm water is more corrosive than cold water. The common practice of grounding electrical connections to water pipes also can increase lead corrosion. Despite these general rules, any kind of water—including hard, soft, acidic, or non-acidic—can contain amounts of lead.
Corrosive water acts to dissolve lead from pipes and solder while the water is in contact with the plumbing. Therefore, lead concentrations in drinking water usually are the highest in the first water out of the tap; they decrease as the water is run. If lead pipes, leaded solder, or brass fixtures are present, even relatively noncorrosive water can dissolve dangerous amounts of lead if the water sits in contact with these materials for an hour or more. Conversely, if your town’s water distribution system and your home plumbing system do not contain lead pipes, lead solder, or brass fixtures, your drinking water probably does not contain significant amounts of lead.
How Much Lead in Water is Too Much?
The Centers for Disease Control suggests that blood lead concentrations over 5 micrograms per deciliter of blood (µg/dL) may indicate lead poisoning. Various studies have found that blood lead concentrations are positively and significantly related to the amount of lead in drinking water. Accounting for other sources of lead exposure (e.g., food, dust), the U.S. EPA set the maximum allowable concentration of lead in public drinking water at 15 µg/L. (Many experts on lead toxicology believe the safe level should be 10 µg/L or less, but for purposes of this discussion we will use the EPA’s level of 15 µg/L.) Since lead serves no beneficial purpose in the human body, it is best if drinking water contains no lead. State drinking water standards must be at least as strict as the EPA drinking water standard of 15 µg/L.
If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. The City is responsible for providing high quality drinking water, but cannot control the variety of materials used in plumbing components. When your water has been sitting for several hours, you can minimize the potential for lead exposure by flushing your tap for 30 seconds to 2 minutes before using water for drinking or cooking. If you are concerned about lead in your water, you may wish to have your water tested. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline (800-426-4791) or at http://water.epa.gov/drink/info/lead/index.cfm.
Can I Filter Lead from Tap Water?
Yes. Commercially available residential filter units are available that will filter both organic and inorganic contaminants in drinking water.
How Much Lead is In Farmington’s Drinking Water?
Farmington tests for lead in its water system every three years in accordance with the Environmental Protection Agency’s Lead and Copper Rule. The most recent results are listed below, and were found to be well below the maximum contaminant level for safe drinking water.