Water System

Boston's early settlers relied on cisterns, wells, and a spring on Boston Common for their water. However, as the city grew, this supply was inadequate and the quality often poor. The first attempt to provide an alternative came from private suppliers who, in 1796, began delivering water from Jamaica Pond through a system of wooden pipes. The City continued to grow in size as well as in population and city planners began to look towards the western part of the state for a more abundant water supply. 

In 1848, the City obtained its first municipal water supply from Long Pond, now called Lake Cochituate, which is about 19 miles west of Boston. The water traveled via the Cochituate Aqueduct into the Brookline Reservoir. At the time, Boston's population was about 127,000 and in the period between 1860 to 1900, the population tripled to 550,000. To meet the increasing water needs, several construction projects were initiated. Beginning in 1866, construction of several reservoirs and related aqueducts were completed. These additions, however, still did not meet the needs of the growing population. In response to this, in 1895, the City formed the Metropolitan Water District (MWD), which was to identify additional water sources for the City.

Looking still farther west, city planners located an area in central Massachusetts, 35 miles west of Boston, called Wachusett. In 1908, the Wachusett Dam, Reservoir and Aqueduct were completed. In 1919, to oversee the complex water system (and storm/sewer system), the Massachusetts Legislature created the Metropolitan District Commission (MDC), now the Department of Conservation and Recreation. 

The MDC developed a large-scale plan for expanding the water supply so that it would meet future growth. The results of this plan were to augment the Wachusett Reservoir by impounding the Swift River with the construction of the Quabbin Reservoir, 65 miles west of Boston. Completed in 1939, the Quabbin Reservoir has a capacity of 412 billion gallons, making it the largest man-made water supply reservoir in the world. To this day, the Quabbin still serves as the major source of water for metropolitan Boston.

By the 1970s, years of deferred maintenance began to take their toll on the water system. Water demand, once again, was beginning to stretch a supply that had not increased significantly in forty years. In addition, water was being lost from leaking pipes before it ever reached the consumer and water pressures were low in many parts of the City. 

In 1977, BWSC was created to oversee and update the City of Boston's system. In 1985, Massachusetts Legislation was enacted that transferred the possession, control, and operation of the MDC Water and Sewerage Divisions to the newly created Massachusetts Water Resources Authority (MWRA). This included the reservoirs and major transmission lines throughout the metropolitan area. 

Boston is one of 51 member communities that purchase water (fluoridated and disinfected) from the Massachusetts Water Resources Authority (MWRA) through 29 active metered connections located at various delivery points. The MWRA obtains its water supply from the Quabbin Reservoir, the Wachusett Reservoir, and the Ware River, which have a combined capacity of approximately 477 billion gallons. The Quabbin Reservoir, located 65 miles west of Boston, has an elevation of approximately 530 feet above the mean elevation of the City. This elevation differential creates a natural gravitational flow through most of the MWRA's waterworks system and thereby eliminates the need to pump water to BWSC's system.

Boston's drinking water comes from two source reservoirs in central and western Massachusetts, the Quabbin and the Wachusett Reservoirs. In addition to the reservoirs, the system includes surface aqueducts, covered storage tanks, treatment facilities, and deep rock tunnels. This system is known as the Metropolitan Boston Water System. The Massachusetts Water Resources Authority (MWRA) and the Department of Conservation and Recreation (DCR) jointly manage the Metropolitan Boston Water System. The MWRA provides treatment and distribution of drinking water to 48 communities in the metropolitan area, including Boston. The DCR manages the lands adjacent to the source reservoirs and is responsible for keeping the reservoirs free from water quality contamination to the greatest extent possible. And finally, BWSC delivers the water to homes and businesses throughout the City of Boston.

Water distributed to the Boston metropolitan area is conveyed from the reservoirs through the Cosgrove or Wachusett Aqueducts and treated at the MWRA's John J. Carroll Water Treatment Plant at Walnut Hill in Marlborough. Treatment includes ozone disinfection, pH adjustment with sodium bicarbonate, and the addition of chloramines and fluoride. Water leaves the plant through the Metrowest Water Supply Tunnel and is stored in covered storage tanks at Norumbega Reservoir and the Loring Road Tanks in Weston, where it is held for delivery to the BWSC service networks. MWRA mains distribute water to the BWSC system at 29 metered delivery points.

Boston’s water system has been designed with a redundant capacity to support most of the major distribution lines. This redundancy permits required maintenance work on discrete parts of the system without interrupting continuous service throughout the City. 

The water system consists of approximately 1,018 linear miles of pipe which range in size from 4 inches to 48 inches, including 12,758 hydrants and 17,725 valves. In addition, there are four major service networks: Southern Low Service, Northern Low Service, Southern High Service, and Southern Extra-High Service. Approximately 90% of the water consumed in the City is delivered through the Southern Low and Southern High Services.

BWSC follows a systematic renewal and replacement program by replacing older cast iron water pipe and rehabilitating pipe through a process of cleaning and cement lining. A minimum of 8 miles of pipe is included in each year's capital program.

Through aggressive leak detection and repair, and progressive metering programs, BWSC continues to reduce its unbilled and unaccounted-for-water. These programs have resulted in a reduction in unbilled water from 70 MGD (millions of gallons a day) in 1977 to 9.26 MGD in 2017. Unbilled water is the difference between water purchased from MWRA and water sold to customers. Much of the unbilled water is used for public purposes, such as for firefighting and street sweeping. BWSC continues to provide a leakage survey of the entire system each year. Leaks are repaired on an immediate basis.

The BWSC and the Massachusetts Water Resources Authority monitor the quality of Boston's drinking water to ensure that it is safe to drink and complies with Federal and State drinking water quality requirements. Read BWSC's annual Drinking Water Quality Report.

The MWRA tests over 1,600 water quality samples per month, from the reservoirs all the way to household taps.  Annual and monthly test results are posted by the MWRA on its website.

BWSC is concerned about lead in drinking water.  Lead in drinking water is rarely the sole cause lead poisoning.  However, it can increase a person's total lead exposure, particularly the exposure to infants who drink baby formulas and concentrated juices that are mixed with water.  Lead enters drinking water primarily as a result of the corrosion, or wearing away, of materials containing lead in the water distribution system and household plumbing.  

Water Quality Report