FAQs

What are Wellesley's sources of drinking water?

The Wellesley municipal water supply comes from ten wells within the town and from the regional Massachusetts Water Resources Authority (MWRA). There are four town wells near Morses Pond and sixtown wells along Rosemary Brook. The water from these wells is treated at the facilities described above. These seven wells vary in depth from 40 to 56 feet. The MWRA gets its water from the Quabbin and Wachusett Reservoirs in central Massachusetts.

What treatment does Wellesley's drinking water receive?

Wellesley treats water from town wells by filtration, aeration, and disinfection. The filtration process includes the chemical addition of chlorine, permanganate, and hydroxide to condition the water for the removal of iron and manganese minerals. The water is then filtered, under pressure, through a bed of anthracite coal, green sand, and garnet sand. After filtration, the water is sent into a tray aerator, where it cascades through a series of redwood slatted trays against a counter current of air. The aeration process is primarily designed to reduce acidity. After aeration, the water is treated with chlorine and passed through a long clearwell channel to insure stabilized disinfection. It is then pumped into the 149 miles of distribution mains that supply the households and businesses of Wellesley. Fluoride is also added to the water.

The MWRA treats its water by disinfection with chlorine at Wachusett Reservoir. At the Marlboro Corrosion Control Facility, the MWRA water is treated with soda ash and carbon dioxide to adjust its alkalinity and its pH. At Norembega Reservoir, the water is further disinfected by chloramination, which is a combination of chlorine and ammonia. Fluoride is also added to the MWRA water.

Where does Wellesley's wastewater go?

Wellesley is part of the Massachusetts Water Resources Authority (MWRA) Wastewater System. Our wastewater, or sewage, is discharged into the MWRA's collection sewers, which flow to the Deer Island Wastewater Treatment Facility. The treatment processes include sedimentation and activated sludge.

The recycled solids from Deer Island are anaerobically digested and delivered to a sludge treatment facility at Fore River. There, the material is heat treated to form a soil enhancement product (fertilizer).

Why is it important not to discharge basement groundwater into the sanitary sewer?

It is prohibited by Town and MWRA regulations to discharge sump pump, or other storm and groundwaters, into the sanitary sewers. This prohibition is important because it reduces the potential of sewer overflows into other people's basements and it allows for proper treatment of the wastewater at the treatment facility. During storm and high groundwater conditions, the sewers receive far too much unnecessary water. This can cause severe problems for others.

Wellesley rate payers pay a very significant cost for treatment of their wastewater. Since there is no need to treat basement groundwater as sewage, every gallon that does not enter the Town's sanitary sewer reduces everyone's sewer bills.

Sump pumps should be connected only to the street storm drainage system, or to proper drainage on the homeowner's property.

How can I learn about the quality of my drinking water?

Each year the Wellesley DPW posts the Water Consumer Awareness Report on the Town's website. This report contains information on the quality of Wellesley's tap water. Any analytes detected in our water monitoring programs will be listed in this report. 

What water quality monitoring is performed by the Town?

Each year there are over 1,600 chemical/biological analyses performed by independent laboratories on our water. In addition, DPW staff perform more than 6,000 chemical analyses per year to insure proper operation of our treatment facilities. The monitoring program includes: Coliform Bacteria, Disinfection Residuals, Disinfection By-Products, Volatile Organic Chemicals, Inorganic Chemicals, Radionuclides, and Synthetic Organic Chemicals.

The Town also participates in the Federal Lead Sampling program which requires scheduled sampling at predetermined locations throughout Wellesley. If your residence is not one of the sampled locations and you would like to determine whether or not you have any lead in your own pipes or fixtures, the MWRA offers this list of laboratories which offer testing for lead in your water. These laboratories can be found at the following link: http://www.mwra.state.ma.us/04water/html/testinglabs.html

Why do you flush hydrants?

Twice each year we flush all the hydrants in our system for two reasons. First, to remove any scaling that may have deposited within the water mains since the last flushing. Second, to exercise the hydrants in order to evaluate each hydrant for its potential need of maintenance.

When are you flushing hydrants?

Typically we flush hydrants the week after Patriot's Day week and the week after Columbus Day week. Operational demands may require that we vary from this schedule, however, this is rarely done (e.g. the last time we varied was due to the record breaking storm of October 20-21, 1996). Whenever we flush hydrants, we mail notices prior to the week of flushing to all customers.

How much fluoride is there in the water?

There are about 0.1 parts per million of naturally occurring fluoride in our groundwater as it is pumped from our wells. By vote of the Townspeople, Wellesley has required the Wellesley DPW to add an additional 0.6 parts per million as part of the treatment process. Therefore your tap water has 0.7 parts per million of fluoride.

What is a cross connection?

A cross connection is any actual or potential connection between a pipe conveying potable water in a public water supply and any non-potable water supply, piping or equipment.

What are examples of cross connections?

Cross connections may include, but are not limited to the following:  irrigation (lawn or farm) piping; fire sprinkler systems; boiler water systems; pipes made of materials not approved to convey potable water; piping from a non-approved source of water such as a private water supply; various hose connections; etc.

What conditions cause cross connection contamination?

Potable water systems can be contaminated by cross connections whenever there is back pressure or siphon conditions at the connection, which thereby cause the backflow of potential contaminants into the potable water system.

What can be done to prevent such backflow?

Elimination of the cross connection whenever practicable is the preferred prevention.  When such elimination is not practicable an approved backflow prevention device may be installed.

What is a backflow prevention device?

There are numerous such devices that may, or may not, include various spring-loaded valves and that may, or may not, be testable under variable conditions of pressure.  State regulations specifically require appropriate devices and the maintenance and operation of such devices depending on the actual or potential conditions of the cross connection.


If you have any other questions, please contact the Water & Sewer Division at (781) 235-7600 x3355, or at dpw@wellesleyma.gov.