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Water Quality FAQs

General Drinking Water Utility Questions

  1. Who makes the rules and regulations for drinking water?
    Regulations are made by both federal and state agencies. The Safe Drinking Water Act (SDWA) passed by Congress in 1974 and amended in 1986 and 1996 is governed by the United States Environmental Protection Agency (USEPA).


  2. I live in an apartment and my water bill is included in my rent. How can I receive information concerning the quality of my tap water?
    The DC Water and Sewer Authority Annual Water Quality Report is sent to all addresses within our distribution system regardless if a bill is received at the address. This report is also available on WASA's water quality homepage along with reports from previous years.


  3. If the water comes from the Potomac River, how are germs and other contaminants removed from the drinking water?
    The water taken from the Potomac River is filtered and disinfected by the Washington Aqueduct to meet safe drinking water standards. The disinfectant residual is strong enough to be maintained throughout the distribution system thus controlling bacteria levels. DCWASA analyzes samples everyday all over the city for bacteria (total coliform) and to ensure that the drinking water retains adequate disinfectant levels. These are just a few of the many drinking water parameters that are analyzed on a daily basis in our laboratories.


  4. Is it okay to use water from the hot water tap for drinking, cooking, or making baby formula?
    Hot water generally comes from a hot water heater that may contain impurities that should not be ingested. Some of these impurities might be metals from household plumbing that are concentrated in the heating process. Additionally, these impurities from the household plumbing dissolve more rapidly in hot water than cold water causing the amount of impurities to be higher in hot water. Therefore, cold water should be used for all drinking and cooking uses, as well as for baby formula.


  5. Do I need to treat the tap water in any way before I place fish in an aquarium?
    Washington, D.C. drinking water has chloramines for disinfection purposes, which can be harmful to fish if not neutralized. Chemical additives with directions for removing chloramines from water for use in fish tanks or ponds are available at pet or fish supply stores.


  6. I have seen work crews cleaning water mains and the water they flush out looks terrible. How can the water be safe if the pipes are so dirty?
    DCWASA's distribution system contains many pipes made out of iron. Most of these pipes have a thin film of rust and a thin biofilm layer containing harmless microbes along the inside wall. Buildup of this material may cause the tap water to be discolored. DCWASA has a regular program of flushing and cleaning the distribution pipes. When all of this material is removed from several miles of pipe and it comes out of a fire hydrant all at once, it looks really dirty at the beginning of the procedure. If you watch our workers flush, you will notice that the water clears up rather quickly.


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Drinking Water Questions

  1. What is chloramine and why is it added to the water?
    Chlorine is added to water at the treatment plant to disinfect the water, which kills harmful bacteria and germs. A small amount of ammonia is added to the chlorinated water before it leaves the treatment plant to create a slightly different disinfectant called Chloramines.

    Chloramines can maintain a disinfectant residual longer than chlorine, which is important for large distribution systems such as the District's (the District contains over 1,300 miles of pipe for distributing drinking water). Chloramine levels in WASA's drinking water vary from about 2 parts per million (ppm) to 3.5 ppm depending on where you live relative to the water treatment plant, as well as the time of the year (chlorine and chloramines are harder to keep in the water during the summer when the temperature of the water is high).

    Chloramine was also chosen because of its capability to minimize potential carcinogenic chlorine byproducts (referred to as disinfection byproducts or DPBs). WASA monitors these byproducts routinely and provides updated information on the Water Quality Home Page


  2. Is the fluoride in my drinking water safe?
    In correct amounts, fluoride has improved the dental health of American consumers. The drinking water in Washington, D.C., generally has between 0.8 and 1.2 mg/L of fluoride.


  3. Is the orthophosphate corrosion inhibitor added to my drinking water safe?
    Orthophosphate is a commonly used "corrosion inhibitor" that is added at the treatment plants. Orthophosphate works by forming a protective coating inside of service line pipes and fixtures in customer's homes to prevent lead from leaching into drinking water. Orthophosphate is a food-grade chemical and is generally recognized as safe by the Food and Drug Administration and the EPA. Updated information on phosphate levels can be found on WASA's Water Quality Home Page.


  4. How "hard" is the water?

    Washington D.C.'s water is "moderately hard," and it may vary throughout the city. Hardness will also vary based on seasonal changes. For example, during a drought the hardness of the water increases as the calcium carbonates in the natural waters become more concentrated. Hardness usually peaks during the warmer months (July – September) and is lower during the cold winter months.

    The hardness of Washington D.C.'s tap water is typically around 70 to 120 parts-per-million, which translates to about 4 to 7 grains per gallon. When using dishwashers, you may notice a slight increase in "spotting" on glassware. You may also notice a light white ring in pots when boiling water. This occurrence usually happens in the summer when hardness is at its highest. This residue consists mainly of calcium carbonate, the same ingredients found in anti-acid products.



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Lead Questions

  1. How does lead enter the water system?
    Lead enters the water supply primarily as a result of corrosion, or the wearing away of materials containing lead in the water distribution system and household plumbing. These materials include lead based solder used to join copper pipe, brass and chrome plated brass faucets, and in some cases, pipes made of lead that connect your house to the water main (service lines).

    When water stands in lead pipes or plumbing systems containing lead for several hours or more, the lead may dissolve into your drinking water. This means the first water drawn from the tap in the morning, or later in the afternoon after returning from work or school, can contain fairly high levels of lead.


  2. What is WASA doing to reduce lead levels?
    Orthophosphate, a common food-grade chemical is being added to the water by the Washington Aqueduct at the treatment plants at a concentration of approximately 2 parts per million (ppm). This chemical was introduced in August 2004 to the water distribution system and has reduced lead concentrations in over 92% of the homes tested to below EPA's action level of less than or equal to 15 ppb. Orthophosphate works by building up a thin protective coating inside pipes and plumbing fixtures to prevent water from corroding pipes which cause metals to leach.


  3. What is a Lead or Copper Action Level?
    An action level is not a health-based standard, but a standard that is used to indicate that a utility may need to install corrosion control treatment. The action level for lead is 0.015 mg/L or 15 ppb or less in 90% of the homes sampled. The action level for copper is 1.3 mg/L or 1300 ppb or less in 90% of the homes sampled.


  4. 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 another high water use activity such as bathing or washing your clothes so that a total of at least 10 minutes of flushing has occured. (The large amount of water used will flush a significant amount of water from your home's pipes)
    • Use only cold water for cooking and drinking.
    • Alternatively, bottled water can be used for drinking and cooking.
  5. For more information about lead in drinking water, click here


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General Drinking Water Questions

  1. Can I talk to someone about my water quality?
    Water is treated at the Washington Aqueduct treatment plants. Water Quality samples are collected continuously to ensure the water leaving the plant meets EPA standards. In addition, WASA collects tap water samples throughout the city on a daily basis, and analyze the samples immediately on-site and at our distribution laboratory. If you have any questions or concerns regarding the quality of your water you may contact the Water Quality Department at 202-612-3440.


  2. All of the strainers in my faucets are clogging with white particles. What could this be?

    Particles can clog aerators and showerheads because of the small screens that often found in these fixtures. These screens may collect particles present in the water. The screens are called aerators because they break up the flow of water as it comes out of the faucet. The particles that get trapped on the aerators can come from a variety of sources. One of the most common sources is the hot water heater.

    These white particles may be pieces of the dip tube from your hot water heater or calcium carbonate, which is natural in the drinking water and will precipitate at high temperatures.

    The dip tube carries the cold water from the top of the hot water heater to the bottom, where the cold water is heated. A dip tube is often made of polypropylene, a nontoxic plastic material. This plastic can break apart or disintegrate, and the small pieces can be carried away in the water to the faucet where they collect on the faucet's aerator. Since it is only a hot water concern, these particles will only be found in places where hot water travels; so the toilet bowls and tanks, and automatic ice maker will not contain these particles if indeed they are from the dip tube. The same faucet delivers both hot and cold water in most homes. That is why material from the hot water heater can clog the cold water faucet.

    Dissolved calcium is naturally found in our drinking water. In the summer time, calcium levels can increase. Calcium will naturally precipitate as calcium carbonate, which is also white, in hot water heaters. In time, calcium carbonate may accumulate at the bottom of the hot water heater.

    To determine if 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 mostly dissolves within 24 hours, it is likely to be calcium carbonate. If no bubbling occurs or the particle is not dissolved, it is probably polypropylene.

    If you are experiencing a calcium carbonate problem it is recommended to flush out your hot water heater.

    If you are experiencing a polypropylene problem, call the manufacturer of your hot water heater for further information.

    If you are not sure of the material you can call WASA's Water Quality Office at 202-612-3440 and speak to a Water Quality Specialist for guidance.



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

    The most common cause of black particles showing up in tap water is the disintegration of rubber materials used in plumbing fixtures. Gaskets and o-rings can disintegrate over time and some pieces can collect in toilet tanks and around faucets. Similar problems are often experienced in newly constructed or renovated buildings, as plumbers inevitably disturb the plumbing system when they do their work. A simple flush through the system may easily remedy the situation.

    For people that use filters, either attached to plumbing or a pitcher, these most often use carbon to filter contaminants from the water. The small carbon particles are also black and can pass through the filters. Typically this occurs when the filter is spent and needs changing.

    Black particles can also come from precipitated iron and manganese, which may come loose from pipewalls after a large main break or major construction.

    If the problem persists after flushing and you have determined that the source is not from a rubber gasket or filter, please contact WASA's Water Quality Department at 202-612-3440.



  4. Why does tap water sometimes look milky or opaque?

    During the time of year when the water coming into the house is colder than the temperature inside the house, this phenomenon can occur. Cold water holds more oxygen than warm water. Consequently, when the cold water from the water mains outside come inside our warm homes, the water begins to warm and the oxygen has to escape. This escaping of the air bubbles makes the water look milky. You can test this by running the water into a clear container and observe for a few minutes. If the water clears from the bottom to the top of the container then you are seeing the air bubbles rising to the surface. The air bubbles are not harmful and will quickly dissipate.

    If the cloudiness is not air bubbles, you should contact WASA's Water Quality Office at 202-612-3440.



  5. My water has a color to it, what should I do?

    If your water has a brownish or rusty color, the color is a result of the presence of iron or rust. Most of the pipes in the District used to deliver water to your home are made of cast iron. Older mains can impart rust to the water. Newer mains are lined with cement to lessen the contact between the water and the iron mains. However, when there is an upset in the system such as a water main break, or when a valve is operated or water flow is changed, rust may be stirred up.

    A rust problem is usually short-lived, and should be gone in a day or less once it is flushed from our water distribution system or your home plumbing. WASA recommends not drinking any water that is discolored. In addition, do not wash clothes when water appears rusty because the rust will stain the fabric. Flush your cold for 15 minutes should clear up the color. If the color does not dissipate after 15 minutes of flushing, contact the Water Quality Department at 202-612-3440 for help with your problem.



  6. Sometimes ice cubes made from the tap water, or the melted water from ice cubes contains white particles. What are these particles and where do they come from?
    Ice cubes freeze from the outside in. Ice is formed from pure water (hydrogen and oxygen) therefore the minerals such as calcium and magnesium normally found in the water sometimes end up as visible particulates in the core of the ice cube. The white particles are not toxic.


  7. What is the white residue sometimes found on items such as coffee pots, shower doors, glassware, and cookware?
    The white residues are minerals that are found in the water such as calcium. Over time and repeated water use there may be a build-up of the minerals on any item the water comes in contact with. There are commercial products that can be purchased to rid the surface of mineral build-up.


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