Drinking Water Quality FAQs


  • Does Cambridge Water monitor chloramine levels?

    CWD routinely monitors the chloramine and chlorine levels throughout the water distribution system. Chloramine levels vary only slightly depending on where you live relative to the water treatment plant. For additional information and updated water quality results for chlorine, please see Water Department Annual Drinking Water Quality report.

  • 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.

  • What is chlorine 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 Cambridge Water Department (CWD), uses ozone and chlorine as primary disinfectants and chloramine as a secondary disinfectant. The U.S. Environmental Protection Agency (EPA) regulates the safe use of chloramine and requires the CWD 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 Cambridge's, which contains more than 190 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.
  • 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. Tap Water and Fish - PDF

    For more information about chloramine, please visit the EPA Web site.

  • 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. CWD'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. CWD recommends not drinking tap water if it is discolored (won't taste good). 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 Distribution Division at 617-349-4770. CWD offers free of charge to Cambridge residents a rust remover product (Red B Gone) available here at the water treatment plant on Fresh Pond. Rust remover products are also available at larger grocery stores in the detergent isle.

  • Why do I sometimes see work crews flushing fire hydrants?

    CWD regularly flushes fire hydrants throughout the distribution system to clean the mains in the streets and remove scale build-up 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?

    Milky or cloudy water is often caused by air that enters pipes and escapes in the form of oxygen bubbles when water leaves your tap. Cloudiness and air bubbles do not present a health risk. During colder months, water in outside pipes is colder and holds more oxygen than your household pipes. Consequently, when the cold water enters your building and begins to warm, the oxygen bubbles escape and cause the water to look milky. Construction in the distribution system can also allow air to enter the pipes and cause the appearance of cloudy water.

    Cloudiness and air bubbles should naturally disappear in a few minutes. You can test this by running the 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 the cloudiness does not disappear, contact the Distribution Division at 617-349-4770.

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

    Aerators are strainers that attach to your faucet or shower head and 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 build up is often white and comes from a variety of sources.

    The most common source of build up 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.

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

    For additional information, contact the Cambridge Water Laboratory at 617-349-4780.

  • 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 disintegration of o-rings and gaskets (within one to two years of installation), contact the manufacturer to request plumbing fixtures that are resistant to chloramine.

    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 Cambridge Water Laboratory at 617-349-4780.

  • 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 Cambridge Water Laboratory  at 617-349-4780.

  • What can I do if my water smells and tastes like chlorine?

    CWD disinfects the drinking water with chlorine and chloramine to ensure protection against contaminants throughout the distribution system and in your home. CWD 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, CWD 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 another high water use activity 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 Cambridge Water Laboratory at 617-349-4780.

  • How "hard" is the water in Cambridge?

    Water hardness refers to the mineral content of water, commonly calcium and magnesium. CWD's water is "slightly hard" and varies only slightly throughout the city. Hardness also varies slightly by seasons of the year.  When using dishwashers, you may notice a slight increase in "spotting" on glassware, flatware or white residue in kitchenware and showers. Using a high quality dishwasher detergent with a rinse agent will solve this problem. This residue consists mainly of calcium carbonate, the same ingredient found in anti-acid products and not a known health risk. The hardness of the city's tap water is typically around 40 to 60 parts per million or 3 to 4 grains per gallon.

  • How does lead enter the water system?

    Lead enters the water from the corrosion of materials containing lead. Although CWD has an aggressive program to eliminate lead service lines there are some still in use and can usually be found in pre-world war II single or small multifamily residences.   Lead service lines that connect your house to the mains in the street, other sources of lead like lead-based solder (pre-1986) 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, the first water you draw from the tap in the morning or after you return home from an absence of several hours may have some detectable levels of lead. 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 CWD doing to reduce lead levels?

    The U.S. Environmental Protection Agency (EPA) requires that water treatment plants ensure treated water does not corrode pipes. CWD is responsible for treating the drinking water in Cambridge, adds the common chemical Sodium hydroxide to reduce pipe corrosion by adjusting the pH of the water. To date, lead concentrations are below EPA's action level of less than or equal to 15 parts per billion. pH adjustment works by creating a thin protective mineral 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. The large amount of water used 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.

  • Is fluoride in Cambridge drinking water?

    CWD adds fluoride to the drinking water supplied to Cambridge to meet an optimal level of 1.0 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. Presently the Massachusetts Department of Public Health (MDPH) has not adopted this recommendation.  The current level of fluoride recommended by MDPH is 0.9 to 1.2 mg/L.  In the past, HHS supported a fluoride level between 0.7 to 1.2 mg/L, as safe and effective in preventing tooth decay. 

  • What is EPA's drinking water standard for fluoride?

    The United States Environmental Protection Agency's (US 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?

    CWD regularly tests the fluoride levels in the distribution system and in the water produced by the water treatment plant. CWD's fluoride data is available in the Water Quality Reports section. The range of CWD's fluoride results from the water treatment plants is included in CWD's Annual Drinking Water Quality Reports.

  • Disinfection byproducts Disinfection byproducts (DBPs)

    Disinfection byproducts (DBPs) form when chlorine and other disinfectants react with naturally occurring materials in Cambridge's surface water supply reservoirs. 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 1990, CWD introduced 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 CWD's Annual Drinking Water Quality Report.

  • 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 Cambridge's surface water supply reservoirs, our source water that is treated and used for drinking in Cambridge.

  • How do pharmaceuticals and other compounds enter Cambridge's surface water supply reservoirs?

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

    The pharmaceuticals we take are not completely absorbed by the body and enter waste water 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.

  • How do pharmaceuticals and other compounds enter Cambridge's surface water supply reservoirs?

    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 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?

    Cambridge has two public prescription drug take-back or collection programs. Cambridge residents can bring unused prescription drugs to the Police Department at 125 Sixth Street or to the Hazardous Waste Collection Days listed on the Public Works Website.  

    For more information on PPCPs visit the EPA Pharmaceuticals and Personal Care Products page.

  • I didn't find an answer to your question about Cambridge Drinking Water?

    Call the Water Quality Laboratory at 617-349-3480, if no answer please leave a message oremail us.