Drinking Water Quality FAQs

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What is chloramine and why is it added to water?

Chloramine is a disinfectant used to treat drinking water and formed when ammonia is added to chlorine. The Washington Aqueduct, responsible for treating the District of Columbia's drinking water, uses chlorine as a primary disinfectant and chloramine as a secondary disinfectant. The U.S. Environmental Protection Agency (EPA) regulates the safe use of chloramine and requires the Washington Aqueduct to meet strict health standards when chloramine is used for drinking water disinfection.

When water from the water treatment plant enters the distribution system, chloramine provides protection against contaminants as it moves through the mains in the streets and reaches your taps. This long-lasting protection is greater than chlorine, which is important for large distribution systems such as Washington, D.C.'s, which contains more than 1,300 miles of pipe for distributing drinking water. Chloramine also lowers the levels of certain byproducts of water disinfection - known as disinfection byproducts (DBPs) - that may lead to health risks.

Does DC Water monitor chloramine levels?
DC Water routinely monitors the chloramine and chlorine levels throughout the water distribution system. Chloramine levels vary depending on where you live relative to the water treatment plant. For additional information and updated water quality results for chlorine, please see Water Quality Test Results.
Is chloramine safe in water used for kidney dialysis?
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.
Can I use tap water treated with chloramine in my fish aquarium?
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. a< href="https://www.dcwater.com/waterquality/Tap_Water_and_Fish.pdf" target="_blank">Tap Water and Fish - PDF.

For more information about chloramine, please visit the EPA website.

Taste, Color, and Odor

My water is brownish in color, what should I do?

If your water is brownish or rusty in color, the cause is likely iron. Iron in drinking water is not a health risk but can cause discoloration and is often the result of aging pipes made of iron. DC Water's distribution system has many pipes made of iron that are known to have fragile iron scales. During water main breaks or construction, interruption of normal water flow and disturbance of pipe walls may release the iron scale and cause discoloration.Discoloration from iron is usually temporary and should disappear after water is flushed from the distribution system or your home 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.

Why do I sometimes see work crews flushing fire hydrants?
DC Water regularly flushes fire hydrants throughout the District of Columbia to clean the mains in the streets and remove scale buildup in 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 rather quickly.
Why does tap water sometimes look milky or cloudy?
Tap water with a milky or cloudy color.

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 household pipes. Consequently, when the cold water enters your building and begins to warm, the oxygen bubbles escape and cause the water to look cloudy or milky. Construction in the distribution system can also allow air to enter the pipes and cause 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 observing 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 you try this and the cloudiness does not disappear after several minutes after collecting a sample of cold water in a clear container, contact the Drinking Water Division at 202-612-3440. One way to remove the air is to run the cold water faucets in all sinks and tubs (after removing the aerators) for 5 minutes starting at the lowest level of the residence.

The strainers in my faucets are clogged with white particles. What could this be?

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 routinely cleaned throughout the year and replaced once a year. Particle buildup is often white and comes from a variety of sources.

Sink aerator clogged with paricles.

The most common source of buildup in aerators is from the hot water heater. The hot water heater dip tube is made of a nontoxic plastic material called polypropylene. This plastic can break apart or disintegrate and travel in hot water to your faucet, eventually collecting in the aerator.

Dissolved calcium is naturally found in our drinking water and can naturally change to calcium carbonate in hot water heaters. Over time, calcium carbonate may accumulate at the bottom of the hot water heater and collect in your aerators.

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, we recommend flushing the hot water heater. Contact a plumber or download instructions for draining your hot water heater (PDF 244 kb) . If you are experiencing a polypropylene problem, call the manufacturer of your hot water heater.

For additional information, contact the Drinking Water Division at 202-612-3440.

Why do I sometimes see black particles in my tap water?

The common cause of black particles in tap water is the disintegration of rubber materials used in plumbing fixtures. Plumbing gaskets and o-rings disintegrate over time and can collect in toilet tanks and around faucets. Similar problems are common in newly constructed or renovated buildings. In addition, the use of chloramine as a disinfectant is known to cause rapid disintegration of some types of plumbing fixtures. If you experience rapid o-ring or gasket disintegration (within one to two years of installation), contact the manufacturer to request chloramine-resistant plumbing fixtures.

If you have filters attached to your plumbing system or a water pitcher that uses carbon filters to remove contaminants, these can also contribute to the presence of black particles. The small carbon particles of these filters are black and can pass through in your water. Black particles can also come from precipitated iron and manganese in water, which may come loose from pipe walls after a large main break or major construction.

Flushing the system and your taps will likely 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.

What is the white residue I sometimes find on cookware, in the shower and even in ice cubes?
White residue is commonly found in showers and kitchenware as 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 in water.
Sometimes I smell an odor from my tap. What could this be?
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 disinfection product 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.
What can I do if my water smells and tastes like chlorine?

The Washington Aqueduct disinfects the drinking water with chlorine and chloramine to ensure protection against contaminants throughout the distribution system and in your home. DC Water routinely collects and analyzes samples throughout the city to ensure chlorine levels are at or below our stringent 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 (dishwasher-safe) 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 conveniently cold for drinking. If a chlorine odor continues after flushing, contact the Drinking Water Division at 202-612-3440.

Water Hardness

How "hard" is the water in the District of Columbia?

Water hardness refers to the mineral content of water, commonly calcium and magnesium. Washington, D.C.'s water is "moderately hard" and may vary throughout the city. Hardness also varies by seasons of the year. Hardness usually peaks during the warmer months (July through September) and is lower during the winter months.

When using dishwashers, you may notice a slight increase in "spotting" on glassware or white residue in kitchenware and showers. This usually occurs in the summer, when hardness is at its highest. This residue consists mainly of calcium carbonate, which is the same ingredient found in antacid products and does not pose a known health risk. Water hardness is measured in parts per million or grains per gallon. 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 table below is provided for reference.


How does lead enter the water system?
Lead enters the water from the corrosion of materials containing lead. Lead service lines that connect your house to the mains in the street, lead-based solder used to join copper pipe, and brass and chrome-plated brass faucets in your home can wear away over time and release lead. When water stands for several hours in lead pipes or lead plumbing fixtures, lead may dissolve in drinking water. If you have lead service lines, your tap water may have higher levels of lead when you first draw water from the tap in the morning or anytime after you have not used the water for several hours. Flushing your water for two minutes when the tap has not been used for several hours can bring in fresh, high-quality water from the distribution system.
What is DC Water doing to reduce lead levels?
The U.S. Environmental Protection Agency (EPA) requires that water treatment plants ensure treated water does not corrode pipes. The Washington Aqueduct, responsible for treating the drinking water in the District of Columbia, adds the common food-grade chemical orthophosphate to reduce pipe corrosion. Introduced in August 2004, orthophosphate has reduced lead concentrations to below EPA's action level of less than or equal to 15 parts per billion. Orthophosphate works by creating a thin, protective coating inside pipes and plumbing fixtures to prevent water from corroding pipes, thus reducing the presence of lead.
What is a Lead and Copper Action Level?
The EPA sets the Lead and Copper Action Level. This is not a health-based standard. Exceeding an action level requires specific changes to drinking water treatment to reduce pipe corrosion or other requirements that a water system must follow. The action level for lead and copper is triggered when the concentration of lead exceeds 15 parts per billion or the concentration of copper exceeds 1300 parts per billion after the water has been sitting in the pipe for at least six hours.
Is there anything I can do to make my water safer if I have a lead service line?

Some steps you can take include:

  • Draw water for drinking or cooking after flushing your cold tap for at least two minutes or after another high-water-use activity such as bathing or washing clothes. This will flush a significant amount of water from your home's pipes and bring in fresh, high-quality water from the distribution system.
  • Use only cold water for drinking and cooking.

For more information about lead in drinking water, click here.

Corrosion Control Treatment & Orthophosphate

What is corrosion control treatment?
Corrosion control treatment is a treatment technique used to prevent pipe corrosion and the presence of metals in drinking water. Drinking water treatment plants, such as the Washington Aqueduct, use corrosion control treatment before water leaves the treatment plant. The Washington Aqueduct adds orthophosphate to prevent corrosion of pipes in the distribution system and in your home. 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 the District of Columbia's water.
Is orthophosphate safe in my drinking water?
Yes, orthophosphate is a commonly used corrosion control treatment and is safe in drinking water. In 2006, the Environmental Protection Agency (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. For additional information and updated test results for orthophosphate, click here.


Is fluoride in DC drinking water?
Yes. 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).
What is the optimal level of fluoride in drinking water?
The optimal level for fluoride is intended to prevent tooth decay and protect public health. In January 2011, the United States Department of Health and Human Services (HHS) issued a revised recommendation for the optimal level of fluoride in drinking water. Based on new research, HHS recommends a fluoride level of 0.7 mg/L as optimal for ensuring public health protection. In the past, HHS supported a fluoride level between 0.7 to 1.2 mg/L, as safe and effective in preventing tooth decay. For more information on the HHS recommendation, please visit the HHS website .
What is EPA's drinking water standard for fluoride?
The United States Environmental Protection Agency's (EPA) maximum contaminant level (MCL) and maximum contaminant level goal (MCLG) for fluoride is 4 mg/L. According to the U.S. EPA, "Some people who drink water containing fluoride in excess of the MCL over many years could get bone disease, including pain and tenderness of the bones. Fluoride in drinking water at half the MCL or more may cause mottling of children's teeth, usually in children less than nine years old. Mottling, also known as dental fluorosis, may include brown staining and/or pitting of the teeth, and occurs only in developing teeth before they erupt from the gums." For more information about fluoride, visit the EPA website.
What is the maximum contaminant level (MCL) and maximum contaminant level goal (MCLG)?
According to the U.S. Environmental Protection Agency, a MCL is the "highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology." A MCLG is the "level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety."
Where can I find fluoride sampling results?
The Washington Aqueduct regularly tests the fluoride levels in the Potomac River supply and in the water produced by its two drinking water treatment plants, Dalecarlia and McMillan. Washington Aqueduct's fluoride data are available on the Washington Aqueduct's Water Quality website. The range of the Washington Aqueduct's fluoride results from the Dalecarlia and McMillan water treatment plants are included in DC Water's Annual Water Quality Reports.


What is chromium?
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.
Is chromium in water a health risk?
Chromium-3 is an essential and nutritional element for humans, particularly for normal glucose, protein, and fat metabolism. Chromium-6 can pose potential health risks to humans when ingested at high levels, including gastrointestinal and carcinogenic effects.
What is the drinking water standard for chromium?

The Environmental Protection Agency (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. The EPA standard for total chromium was established in 1991 based on the best available science to protect public health.

In 2008, EPA began to review chromium-6 health effects and in September 2010, released a draft scientific assessment. When this report is finalized, EPA will review the conclusions and determine if a standard for chromium-6 is necessary for public health protection. For more information on EPA's investigation of the health effects of chromium, visit the EPA Website.

Is chromium found in District drinking water?

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. Total chromium levels are reported in the Annual Drinking Water Quality Report.

Is DC Water testing for chromium-6?

In February 2011, DC Water and the Washington Aqueduct began voluntarily testing for chromium-6 on a quarterly schedule. The Washington Aqueduct collects samples from the source water (Potomac River) and finished treated water. DC Water collects samples from eight sites in the District's distribution system. Samples are tested at an EPA-certified laboratory. Chromium-6 is found at extremely low levels - parts per billion (ppb) - in District water. A single part per billion is equivalent to one gallon of water in 1,514 Olympic size swimming pools. To view chromium-6 monitoring results, see DC Water Test Results and Washington Aqueduct Test Results. For more information about chromium, visit the EPA website.


What is perchlorate?
Perchlorate is both a naturally occurring and man-made chemical, and scientific research indicates that it may impact the normal function of the thyroid, which produces important developmental hormones. Thyroid hormones are critical to the normal development and growth of fetuses, infants and children. Based on this potential concern, EPA will move forward with proposing a formal rule. This process will include receiving input from key stakeholders as well as submitting any formal rule to a public comment process.
Does the US EPA regulate perchlorate?

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 decision to develop the first national standard for perchlorate reverses a decision made in 2008 by the previous EPA administration. This follows a thorough review by the agency of the emerging science of perchlorate and consideration of input from almost 39,000 public comments.

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.
Is there perchlorate in the District's tap water?
Washington Aqueduct regularly tests for perchlorate in the water produced by its two drinking water treatment plants, Dalecarlia and McMillan. These findings are reported to DC Water and are included in DC Water's Annual Drinking Water Quality Report. For more information on perchlorate, visit the the EPA website.

Disinfection byproducts (DBPs)

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 Environmental Protection Agency (EPA) enforces regulatory limits for two groups of DBPs linked to health risks, known as total trihalomethanes (TTHM) and five haloacetic acids (HAA5).

In 2000, the Washington Aqueduct switched from the use of chlorine to chloramine to reduce DBP levels and comply with EPA's strict standards. This treatment change caused a significant decline in regulated DBP concentrations. For additional information and updated water quality results for DBPs, please see Water Quality Test Results.

Hydraulic Fracturing or "Fracking"

What is "fracking"?
Hydraulic fracturing, or "fracking" is the term applied to the practice by natural gas producers of flooding underground gas deposits with water to break rock and force the gas up to be captured. Fracking is used to collect natural gas from sources such as coalbeds and shale gas formations. Fracking is also used for other applications including oil recovery. During the process, operators pump at least a million gallons of water per well, deep into the earth to break layers of rock and release gas.
What are the concerns about the fracking process?
The two major concerns are related to the environment and to public health. During the fracking process, the injected water may extract naturally occurring salts and minerals that lie deep underground. Some of these minerals can be toxic and may require treatment.
After the process is complete, this used water, called "flowback," is sucked back out. In addition to the salts and minerals, the flowback may also contain small amounts of chemicals added to enhance drilling.
Flowback must be disposed of - options include discharging it into surface water or underground injection. Surface water discharges of the flowback are regulated by the National Pollutant Discharge Elimination System (NPDES) program, which requires flowback to be treated prior to discharge into surface water or underground injection prior to discharge. Treatment is typically performed by wastewater treatment facilities. (EPA: http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/wells_hydrowhat.cfm)
The first concern is that when the flowback is successfully captured, it may not be sent to a wastewater treatment facility to be treated. Critics fear that the water may be illegally dumped or not fully treated.
In addition, some fear that the flowback may escape into the nearby environment without being captured for treatment and will pollute groundwater, or wells for drinking. This is not the case for District drinking water, which comes from a surface water source, the Potomac River - not found to be vulnerable to the risks of fracking.
Does my drinking water contain water used in fracking?
No, the District of Columbia's drinking water is purchased from the Washington Aqueduct, a unit of the United States Army Corps of Engineers, and comes from the Potomac. Their intakes of water are located at Great Falls and Little Falls, where the water flows at a rate of several billion gallons per day. (This enormous flow dilutes any elements that may have entered the river upstream.) Drinking water is then treated at the Aqueduct for distribution to the District and other neighboring jurisdictions. The greater concern to drinking water supplies is the potential for the water used in fracking to enter groundwater-underground water sources such as aquifers-and wells.
Does the Blue Plains Advanced Wastewater Treatment Plant accept water from fracking operations?
  1. No, Blue Plains does not currently accept the hauled flowback from fracking operations, nor have we been approached to accept flowback.
  2. DC Water has not permitted any entity to dispose of flowback from fracking operations into our sewer system, nor have we been approached to do so.
How is fracking regulated?
Water is an important component of the hydraulic fracturing process. The United States Environmental Protection Agency (U.S. EPA) Office of Water regulates waste disposal of flowback and sometimes the injection of fracturing fluids as authorized by the Safe Drinking Water Act and Clean Water Act.
The process has recently gained national attention and with it, scrutiny. The U.S. EPA commissioned a study in 2010. EPA expects to initiate the study in early 2011 and to have the initial study results available by late 2012. This study will look at the potential adverse impact of the practice on drinking water and public health.
For more information, please visit the US EPA website: http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/index.cfm

Pharmaceuticals and Personal Care Products (PPCPs)

What are pharmaceuticals and other emerging contaminants?
Pharmaceuticals found in water are prescription drugs or over-the-counter drugs used by humans and animals. In addition, personal care products (fragrances, cosmetics, lotions, and other compounds) and the broad range of substances we use daily can enter the environment and eventually find its way into the Potomac River, our source water that is treated and used for drinking in Washington, D.C.
How do pharmaceuticals and other compounds enter the Potomac River?

Pharmaceuticals, personal care products, and other compounds are found at extremely low levels in water. Human, animal, agricultural, and other activities can affect the Potomac River. We are all responsible for contaminants found in water.

The pharmaceuticals we take are not completely absorbed by the body and enter wastewater during excretion. Directly flushing pharmaceuticals also adds to its presence in the source water. Herbicides, pesticides, and other compounds used in agriculture and farming industries run off into source waters.

Why are more pharmaceuticals and other compounds being detected in water?
With advancements in technology, a more diverse group of compounds is found at extremely low levels in water. Improved detection and increased use of pharmaceuticals contribute to levels found in parts per billion and parts per trillion. It is likely that these low-level compounds have been present in our water for as long as humans have been using them. The difference is that now technology can detect them.
What does the detection of low levels mean?
Low levels of pharmaceuticals and other compounds found in parts per billion and parts per trillion are below levels known to harm human health. Advances in research and technology improve our understanding of the types and levels of chemicals present in water across the United States and to date do not show evidence of risks to human health.
How should I properly dispose of unused pharmaceuticals?
At this time, the District of Columbia has no public drug take-back or collection programs, but there are alternatives to flushing those pharmaceuticals down the toilet or drain. The Office of National Drug Control Policy recommends the following:
  1. Take your prescription drugs out of their original containers.
  2. Mix drugs with a substance undesired by children and animals, such as cat litter or used coffee grounds.
  3. Put the mixture into a disposable container with a lid, such as an empty margarine tub, or into a sealable bag.
  4. Conceal or remove any personal information, including Rx number, on the empty containers by covering it with black permanent marker or duct tape, or by scratching it off.
  5. Place the sealed container with the mixture, and the empty drug containers, in the trash.

Check out DC Water's Q&A on Pharmaceuticals and Emerging Contaminants in Drinking Water (PDF 232 kb) .

For more information on PPCPs visit the EPA Pharmaceuticals and Personal Care Products page, or download the the National Association of Clean Water Agencies report on pharmaceuticals in drinking water (PDF 421 kb) .

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