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Frequently Asked Questions about Drinking Water
Massachusetts Water Resources Authority


Water in a glass photo

Common concerns:
"Hard" or "soft" water
Yellowish water
Rusty water
Green stains on plumbing fixtures
Pink stains on plumbing fixtures
Cloudy water
Fishy or earthy smell
Chlorine smell
pH of water
Is bacteria in my water?
I have more questions

MWRA treats and tests your drinking water according to strict state and federal standards.

We report test results to government and public health officials and post them on this website. We also mail an annual water quality report to every home and business we serve.

Systems are in place to quickly notify our customers, local government officials, public health agencies and others if your water ever became unsafe to drink.

Because drinking water is a natural resource, its taste, color and odor can sometimes vary slightly from day to day, from town to town and from faucet to faucet.

MWRA's drinking water is treated according to strict state and federal standards so that it is safe to drink.

Here are some answers to some frequently asked questions about drinking water.


I have heard about manganese and water. Is it a concern? What do you find in the water?

Manganese is a common naturally-occurring mineral found in rocks, soil, groundwater, and surface water.  Most water has small amounts of manganese in it. 

The US Environmental Protection Agency (EPA) and Massachusetts Department of Environmental Protection (MA DEP) have set an aesthetics-based secondary standard for manganese in drinking water of 50 parts per billion (ppb). This is not a health standard.  At levels greater than 50 ppb, the water may appear brown, taste unpleasant and may leave black stains on bathroom fixtures and laundry.  MA DEP has recently introduced a health advisory for manganese of 300 ppb.  Manganese is an essential nutrient, but DEP’s health advisory suggests that infants not be fed formula made with water containing levels higher than 300 ppb of manganese.   

MWRA finds very low levels of manganese in the water, usually around 5-10 ppb, which is 5 to 10 times lower than the aesthetic standard and 30 to 60 times lower than the DEP advisory level.  MWRA has never exceeded either the secondary standard of 50 ppb or the health advisory of 300 ppb. 

For more information on water quality and to see current manganese levels, please go to our monthly water quality report.

Visit the DEP web site for more information on DEP’s advisory on manganese (PDF).


Is MWRA drinking water hard or soft?

MWRA's drinking water is soft. If you are an MWRA customer, you probably don't need to use special water softeners for your clothes- or dishwashing machines.

Water's "hardness" and "softness" is due to its concentration of minerals –calcium and magnesium. The lower the mineral concentration, the softer the water is. MWRA's drinking water has a hardness of approximately 16 milligrams per liter, or 1 grain per gallon.

Using water that is considered soft, you do not need to use as much dishwashing soap, laundry detergent, or other soaps. Many new dishwashers allow you to set the hardness of the water so that you do not need to use as much soap in comparison to areas that have hard water.

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In winter, we sometimes get yellowish-looking water from our taps. It stains our bathroom and kitchen fixtures and also our laundry. Why is this happening? Is it safe to use? How can we remove the stains?

MWRA water, which comes from the Quabbin and Wachusett Reservoirs, sometimes turns yellowish from low levels of dissolved iron picked up from old iron pipes in both our system and your community's water system. This mainly occurs in winter, when water usage is low, because the water sits in the pipes for a longer period of time. The water may not be aesthetically pleasing, but according to the federal Environmental Protection Agency (EPA), increased levels of iron that produce yellow water are not public health threats. Hardware stores have inexpensive products to remove rust stains from clothing and household surfaces. MWRA and customer communities replace or rehabilitate old pipes a few miles at a time, an expensive and time-consuming process. Long term solutions take time, but we are constantly cleaning and replacing as much pipe as we can.

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From time to time I get rusty-looking water at home. Sometimes I can even see little specks of rust floating in the water. What is the cause of this, and what should I do when it happens?

Red water, named after the red or black rust specks you asked about, sometimes occurs when there is an increase or change in water flow, largely caused by water main breaks, fire hydrant activations, and flow direction changes made by local towns. These occurrences knock off small particles of rust and stir up sediments in the pipes. It is a temporary condition that usually clears up in a couple of hours. Your local water department should know what is happening at that particular time, and how long the condition should last. If possible, you should refrain from using water -- for laundry, dishes, cooking and drinking -- until the condition clears up.

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We're getting green stains on our bathtub. Someone told us it's a result of copper piping. What is MWRA doing about this?

Green stains on plumbing fixtures are indeed a result of copper leaching from the plumbing in your house. This is a not usually a problem for MWRA communities, although the problem may occur from time to time. MWRA does adjust the pH of the water to reduce the tendency of copper and lead to leach into your drinking water.

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From time to time, I get pink stains in my bathroom, laundry room, or kitchen sink.  What is the cause of these stains and how can I get rid of them?

These pink stains are usually caused by biofilms, and are not harmful.  The pink growth is not from the water, but from bacteria or other microorganisms in the air that thrive in damp areas.  It is mostly observed in the area between water and air, in locations that stay moist.  Biofilms can also be found in shades of yellow or brown, orange, or red.  Because they thrive in the presence of water and small amounts of nutrients, biofilms are found virtually everywhere there is water, including sinks, toilets, shower curtains, humidifiers, ice makers, and water  purification systems.

Scrubbing and chlorine bleach are the best solutions to eliminate the occurrence of the pink residue.   An easy way to do this is to stir three to five tablespoons of bleach to the toilet tank, flush the toilet to allow the bowl to be disinfected, and add another dose of bleach to the tank as it is refilling.  By keeping bathtubs and sinks wiped down and dry, the formation of pink residue can be avoided.

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The hot and cold water from our kitchen sink sometimes comes out very cloudy. If we leave the water in the container, it then clears up quickly and the cloudiness disappears. Should we be using this water, even after it turns clear?

White water turning clear

Cloudy water, also known as white water, is caused by air bubbles in the water. It usually happens when it is very cold outside and air gets mixed in with the water supply. It is completely harmless. The best thing to do is let it sit in an open container until the bubbles naturally disappear.

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In spring and fall, we sometimes notice a fishy or earthy taste and odor to our water. What causes this, and is it safe to drink?

This is probably the result of algae growth in one of the water system's reservoirs, partially caused by the change of season. Different types of algae can cause your water to smell fishy, moldy, grassy or even like cucumbers or violets. Refrigerating the water can help eliminate the odor, and adding a slice of lemon will remove any bitter taste.

In the meantime, when a funny taste or smell is first detected in the water supply, MWRA moves quickly to correct the problem with a limited application of copper sulfate to control the natural algal growth in the affected reservoir. That eventually solves the problem.

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In summer my water smells like chlorine. Why does this happen, and how can reduce the odor?

MWRA, like all water suppliers, disinfects its water to protect against harmful bacteria (from birds, animals, and even humans) that can enter into reservoirs. MWRA uses ozone to kill any harmful bacteria at the CWTP in Marlborough.  Ozone leaves no taste or odor, and in fact improves the natural taste of the water.  To protect the water as it travels through the miles of pipe to get to your house, MWRA uses a mild disinfectant called mono-chloramine that has very little taste or odor.  Occasionally those with a sensitive palette may find their water has the odor of chlorine. It usually doesn't last long, and is related to the normal adjustment of the mono-chloramine treatment. This is more likely in the summer when water is warmer. Chilling the water usually eliminates it. You can leave a pitcher of water in the refrigerator.

If you do use a pitcher or water bottle – don’t forget to wash it occasionally.

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What is the pH of MWRA drinking water?

MWRA treats its drinking water so that it has a pH of approximately 9.3, a slightly alkaline measurement. This pH level helps prevent water from picking up any metal particles that might be in your household plumbing.

Untreated, "raw" water in MWRA's Quabbin Reservoir has a pH of approximately 6.8, close to neutral.

pH measures the amount of hydrogen ion activity in a substance. The pH scale is relative and runs from 0 to 14. 0 is the lowest, and most acidic, pH level. 7 is neutral. 14 is the highest, and most alkaline, pH level.

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Is there sodium in MWRA drinking water?

MWRA tests for sodium regularly and the highest level found was 33.4 milligrams per liter (about 7 milligrams per glass). This is considered to be a very low level of sodium by the FDA. Sodium in water contributes only a small fraction of a person's overall sodium intake.

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What does MWRA do about bacteria in drinking water?

Bacteria are everywhere we go in the world, but there are certain types of bacteria we don't want to see in our water supply, because of public health concerns. Communities regularly take water samples, which are then analyzed in laboratories for bacteria counts. A particular type of bacteria that they test for -- coliform -- serves to indicate that harmful germs may also be present. If coliform are found in 5% or more of the samples collected in a month, the community is required by law to notify residents in their locale. In addition, when coliform are found in samples, the lab conducts additional testing to determine if a specific type, E. coli, is present. If E.coli is present, this is considered evidence of a critical public health concern. Usually the solution in this case is to boil the water until the problem is solved.

MWRA, the Mass. Department of Conservation and Recreation (DCR), and others work hard to assure protection of area reservoirs, especially against birds, dogs, other animals and even swimmers getting into water supplies. Recent improvements to water testing and reporting will permit greater confidence in the future that our water is free from contamination.

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I still have questions. Whom should I call?

If you have a question or concern about your water quality, contact our water quality hotline (617) 242-5323 or email Joshua Das, Public Health Manager.

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Updated January 16, 2014