Sewage Backups

September 9, 2021

Sewage Backups

From time to time, the Town experiences rainfall events that produce excessive amounts of runoff which, in turn, causes flooding and raises the groundwater table. These conditions can lead to sewage backups. Rainfall events are unpredictable, as are the runoff amounts that they may produce. Typically, when the local weather forecast is predicting flash flooding, sewage backups should be expected. Sewage backups occur when excessive stormwater runoff from storm events enters the sanitary sewer system from 1. Elevated groundwater that enters the sewer pipes from the outside. 2. Illegal sump pump discharges and/or other direct stormwater connections to the sanitary sewer. The stormwater volume can be several times greater than the typical sanitary sewage volume. This excessive volume exceeds the design carrying capacity of the sewer pipes causing backups (called surcharging). As the sewers surcharge, the sewage backs up and enters the private sewer connection pipes that extend from each house and business to the main sewer in the street. Once the sewage backup enters the connection, it will find its way into a house or a business through floor drains, washing machine discharges, basement toilets, etc.

In the event of a sewage backup, the property owner should contact their insurance carrier and make their own arrangements for cleanup, property damage repair/replacement, etc. Except for instances where a backup occurs due to the Town's proven negligence, neither the Town nor its insurer is responsible for the costs of cleanup, repair, or replacement of private property.

To prevent sewage backups in houses and businesses, the installation of an automatic check valve in the sewer connection pipe is recommended. These check valves, when installed properly, will prevent sewage from backing up into the house/business when the sewers surcharge. Check valves are installed and paid for by the property owner. Local plumbers and pipe contractors are well-suited for installing check valves and related work. The downside to the automatic check valve is that it will prevent sewage discharge from the house or business until the sewage backup subsides, which could take several hours. In situations where sewer service must be maintained, the property owner should consider the installation of a pumping station. Pumping stations will prevent sewage backups and ensure sewage disposal is always available. However, pumping stations can be costly, have ongoing operations and maintenance costs, and will need a generator to continue functioning if the power is interrupted.

Paul A. Sylvia, P.E.
Superintendent of Water and Sewer
Office of 
The Board of
Water and Sewer Commissioners

3249 County Street
Somerset, Massachusetts 02726
Office 508-679-2731
Plant 508-674-4215