Frozen water is 9% lighter than regular water. That is the reason ice floats.
The purpose of the Boston Water and Sewer Commission's Downspout Disconnection Program is to identify and disconnect downspouts (also known as roof leaders) that discharge into the sanitary sewer system. Downspouts carry stormwater from roofs, which does not need to be treated. The sanitary sewer system is designed to carry domestic and industrial waste from toilets, sinks, showers, dishwashers and washing machines to the MWRA's Deer Island Treatment Plant. The stormwater not only takes up space in the sanitary pipes, but treating it when it doesn't need to be creates an additional expense for ratepayers.
Disconnecting downspouts reduces the amount of stormwater in sanitary sewers during heavy rainfall or snowmelt causing combined sewer overflows (CSO) – combined sanitary waste and stormwater discharged to a local water body when there is not enough space in the pipe for all the flow. The program will reduce the number of CSOs leading to cleaner water in Boston Harbor.
The program is only available in selected neighborhoods of Boston where downspouts have been confirmed as discharging to the sanitary sewer system. Property owners will receive a letter and waiver in the mail with instructions on how to proceed. They can choose to have their downspouts disconnected by BWSC's licensed contractor at no charge, or they can hire their own licensed contractor to do the work at their own expense. The pipes will either be splashed on the ground to allow the water to recharge ground water, or they will be attached to a storm drain in the street. BWSC must be notified in 90 days that the work has been completed, so Commission staff can verify the work. See our Downspout Disconnection brochure for more information.