Drinking Water Quality FAQs

If lead is present in your drinking water, if you have pipes or plumbing fixtures that contain lead, or if you don’t know the material type, you should take steps to minimize potential lead exposure until all sources of lead have been removed. Flush your pipes before using any tap water for drinking or cooking. Run the water until it becomes as cold as it will get and then allow it to run for an additional one to two minutes. Use only cold water for drinking and cooking. You may also choose to filter your water. If you are pregnant, nursing or have children under age six, DC Water recommends that you filter your water before drinking and cooking until all sources of lead have been removed. This includes water used for making infant formula, beverages, and ice.

Please visit our minimizing lead exposure page for more detailed information on how to minimize your exposure to lead.

Brownish or rusty colored water is usually caused by iron. Iron in drinking water is not a health risk. DC Water's distribution system has many pipes made of iron that are known to have iron corrosion scales. During water main breaks or construction, water flow is interrupted and pipes are disturbed which can release the iron scale and cause discoloration. This discoloration usually temporary and should disappear after water is flushed from the system or your plumbing.

DC Water recommends not drinking tap water if it is discolored. In addition, do not wash clothes when water appears rusty, because the rust can stain fabric. Flushing your cold water tap for 15 minutes should clear up discolored water. If the color does not disappear after 15 minutes of flushing, contact the Drinking Water Division at 202-612-3440.

Milky or cloudy water is often caused by oxygen bubbles in the pipes that are released when water leaves the tap. Cloudiness and air bubbles do not present a health risk. During colder months, water in outdoor pipes is colder and holds more oxygen than water in indoor pipes. When the cold water enters a building and gets warmer, the oxygen bubbles escape causing the water to look cloudy or milky. Construction can also allow air to enter the pipes causing the appearance of cloudy water. Hot water can sometimes be cloudy due to dissolved gases in the water escaping as the water is heated. Cloudiness and air bubbles should naturally disappear in a few minutes.

You can test this by running the cold water into a clear container and watching it for a few minutes. If the water clears from the bottom to the top of the container, air bubbles are rising to the surface. If the cloudiness does not disappear after several minutes, contact the Drinking Water Division at 202-612-3440. One way to remove the air from plumbing is to remove any aerators and run the cold water faucets in all sinks and tubs for 5 minutes starting at the lowest level of a building.

The most common cause of black particles in tap water is the breakdown of rubber materials used in plumbing fixtures. The use of chloramine as a disinfectant may cause some types of plumbing fixtures to break down faster than normal. If you experience rapid o-ring or gasket disintegration within a few years of installation, install chloramine-resistant plumbing fixtures.

Carbon filters attached to plumbing fixtures or used in water pitchers can also cause the presence of black particles. The small carbon particles in these filters are black and can pass through in your water. Black particles can also come from iron and manganese in the water, which may come loose from pipe walls after a large main break or major construction.

Flushing the system and your taps should resolve the issue of black particles caused by plumbing fixtures or construction. If black particles are from your filter, you should replace the filter as recommended by the manufacturer. If the problem continues after flushing and you have determined that the source is not a rubber gasket or filter, please contact the Drinking Water Division at 202-612-3440.

An odor from your tap is commonly from the sink drain and not the water. The plumbing beneath your sink, typically the u-shape pipe, can collect debris over time and create an odor at your tap. If you smell an odor, fill a clean glass halfway with tap water and smell the water in a separate room or outdoors. If the odor is no longer present, the odor is likely from the plumbing beneath your sink. We recommend pouring bleach or a disinfectant down your drain to remove any debris and odor. If the odor is not from the sink or the problem persists, contact the Drinking Water Division at 202-612-3440.

Aerators are strainers attached to your faucet or showerhead that break up the flow of water as it leaves your tap. Aerator screens can collect particles found in water and should be cleaned regularly and replaced annually. Particle buildup is often white and comes from a variety of sources, the most common being polypropylene, a nontoxic plastic, breaking down from your hot water heater and dissolved calcium.

To determine whether the material is calcium carbonate or polypropylene, place the material in a small amount of distilled vinegar. If the particle begins to bubble within a few minutes or is mostly dissolved within 24 hours, it is likely calcium carbonate. If no bubbling occurs or the particle does not dissolve, it is likely polypropylene. If you are experiencing a calcium carbonate problem, you should flush your hot water heater. Contact a plumber or download instructions for draining your hot water heater. If you are experiencing a polypropylene problem, call the manufacturer of your hot water heater.

White residue found in showers and on kitchenware is usually the result of dissolved minerals found in water, such as calcium and magnesium. Mineral particles can also be visible in ice cubes made with tap water. These minerals are not a risk to human health but can build up on surfaces over time. Commercial products are available to remove white residue caused by minerals.

Water hardness refers to the mineral content of water, commonly calcium and magnesium. Washington, D.C.'s water is moderately hard, but may vary throughout the city and by seasons of the year. Hardness usually peaks during the warmer months and is lower during the winter months. When using dishwashers, you may notice a slight increase in spotting on glassware or white residue on kitchenware and showers in warmer months. The hardness of the city's tap water is typically around 70 to 120 parts per million or 3 to 9 grains per gallon.

The Washington Aqueduct disinfects the drinking water with chlorine and chloramine to protect against contaminants. DC Water routinely collects and analyzes samples throughout the city to ensure chlorine levels are at or below our target level. However, at times customers may notice an increase in chlorine taste and odor. A chlorine odor is often an indicator that the disinfectant is effectively working to remove bacteria and debris in your pipes.

If you are experiencing a chlorine odor, DC Water recommends flushing your cold water taps for 5-10 minutes for three days to eliminate the odor and remove any bacteria and debris. If you experience a chlorine taste, we recommend collecting and refrigerating cold water after running your cold tap for at least two minutes or after high water use activities such as bathing or washing clothes. Use clean, sterile bottles or pitchers for collecting cold tap water and refrigerate in an open container. Within a few hours, the chlorine taste and odor will disappear and the water will be cold for drinking. If a chlorine odor continues after flushing, contact the Drinking Water Division at 202-612-3440.

Please visit the lead information section for more information about lead and drinking water.

Corrosion control treatment is used to prevent pipe corrosion and the presence of metals in drinking water. Drinking water treatment plants such as the Washington Aqueduct add orthophosphate, a corrosion control treatment, before water leaves the treatment plant. Orthophosphate creates a thin protective coating inside pipes and plumbing fixtures and is very effective in reducing the presence of lead and other metals in drinking water.

Yes, orthophosphate is safe in drinking water. In 2006, the EPA designated orthophosphate treatment as the optimal corrosion control treatment for reducing the presence of lead in drinking water. Orthophosphate is a food-grade chemical that is considered safe by the Food and Drug Administration and the EPA. DC Water has set strict target levels for orthophosphate in the water distribution system and routinely tests the water to ensure levels meet these standards. 

Disinfection byproducts (DBPs) form when chlorine and other disinfectants react with naturally occurring materials in the Potomac River. Long-term exposure to DBPs may be harmful to human health. As a result, the EPA enforces regulatory limits for two groups of DBPs linked to health risks, known as total trihalomethanes (TTHM) and five haloacetic acids (HAA5).

Chloramine is a disinfectant used to treat drinking water that is formed when ammonia is added to chlorine. The Washington Aqueduct, the treatment plant responsible for treating the District of Columbia's drinking water, uses chlorine as a primary disinfectant and chloramine as a secondary disinfectant.

Chloramine provides long lasting protection against contaminants as it moves through the water mains in the streets and reaches the taps. This is important for large distribution systems such as Washington, D.C.'s. Chloramine also lowers the levels of certain byproducts of water disinfection. DC Water routinely monitors the chloramine and chlorine levels throughout the water distribution system.

No, chloramine must be removed from water used for kidney dialysis. Please contact your physician or kidney dialysis center for the appropriate water treatment process.

No, water treated with chloramine can be harmful to fish. Chemical additives are available for removing chloramine from water used in fish tanks or ponds. Contact your local pet store for the appropriate water treatment for fish tanks.

Perchlorate is a naturally occurring and man-made chemical. Scientific research indicates that it may impact the normal function of the thyroid, which produces important developmental hormones critical to the normal development and growth of fetuses, infants and children.

On February 2, 2011, the U.S. EPA reached a decision to develop a regulation for perchlorate to protect Americans from any potential health impacts, while also continuing to take steps to ensure the quality of the water they drink. The EPA will continue to evaluate the science on perchlorate health effects and occurrence in public water systems. The agency will also evaluate the feasibility and affordability of treatment technologies to remove perchlorate and will examine the costs and benefits of potential standards.

Washington Aqueduct regularly tests for perchlorate in the water produced by its two drinking water treatment plants, Dalecarlia and McMillan. For water quality results for perchlorate, please review the latest Water Quality Test Results

Chromium is a naturally occurring metal found in soils, plants, rocks, water and animals. It can be found in water primarily in two forms, chromium-3 (trivalent chromium) and chromium-6 (hexavalent chromium). Chromium-3 occurs naturally in many vegetables, fruits, meats, grains and yeast. Chromium-6 is generally produced by industrial processes, such as steel and pulp mills. Chromium-3 is an essential and nutritional element for humans, particularly for normal glucose, protein, and fat metabolism. Chromium-6 can potentially health risks to humans when ingested at high levels.

Total chromium levels in District drinking water range from zero to 4 parts per billion. On average, these levels are 50 times less than the EPA standard. The Washington Aqueduct is responsible for drinking water treatment and regulatory testing for total chromium. 

The EPA drinking water standard for total chromium is 100 parts per billion (ppb). Total chromium includes chromium-3 and chromium-6. Currently, individual drinking water standards do not exist for chromium-3 or chromium-6.

Almost all water contains some naturally-occurring fluoride, but usually at levels too low to prevent tooth decay. Many communities adjust the fluoride concentration in the water supply to a level known to reduce tooth decay and promote good oral health (often called the optimal level). The Washington Aqueduct adds fluoride to the drinking water supplied to the District of Columbia to meet an optimal level of 0.7 milligrams per liter (mg/L).

DC Water regularly flushes fire hydrants throughout the District of Columbia to clean the mains in the streets and remove scale buildup from pipes. When crews flush hydrants and remove this material from the hydrant and several miles of pipe, it comes out of a hydrant all at once, and the water may initially look discolored. If you watch our workers flush, you will notice that the water clears up quickly.