Plumbers in Somerville, MA

Triple-deckers, two-families and plumbing shared between floors

Of Somerville's 37,756 housing units, 59% were built in 1939 or earlier, so many that the Census can't pin down a median year beyond that oldest bracket. The building mix tells the rest of the story. More than half of all homes (55.2%) sit in buildings of two to four units: 28.2% in two-families and 27.0% in buildings of three or four units, the Census category that takes in the city's triple-deckers. Fewer than 11% are detached single-family houses.

Stacked housing changes how plumbing problems behave. Units piled one above another usually share a drain stack and a building sewer, so a slow drain on the third floor can turn into a ceiling stain on the first, and a blocked main line can back up into whichever fixture sits lowest. With 65.8% of households renting, the first call often goes to a landlord or the condo trustees, and it helps to settle which pipes are common and which belong to a unit before anyone opens a wall. For water showing up where it shouldn't, see our leak detection page.

Combined sewers, Alewife Brook and the Poplar Street pump station

In the city's words, the majority of Somerville is served by a combined sewer system, with sewage and stormwater sharing the same pipes; as of 2022 only about 10% of it had been separated. Two outfalls let the overflow out in storms. SOM001A discharges untreated to Alewife Brook, and SOM007A/MWRA205A sends treated flow to the Mystic River. Somerville posts a public notice each time one discharges and lets residents subscribe; the latest listed as of October 2026 was at SOM001A on July 22, 2026.

Street flooding is the other half of the problem. The city says its drainage system lacks the capacity for short, intense storms, and that flooded streets can push sewage back through the pipes into basements; sea-level rise and storm surge on the Mystic add to the future risk. It advises any home with a basement drain or a basement apartment to get a backflow preventer put in by a plumber. Photos of flooding can be sent to [email protected].

The biggest local fix is the Poplar Street Pump Station at 10 Poplar Street, meant to cut flooding in Wards 2 and 3 and reduce overflows. Construction began in spring 2023 and is scheduled through 2027. Its 4-million-gallon storage tank was finished in 2025, and the spring 2026 project update reported the pumps installed, with capacity to move up to 50 million gallons a day. Longer term, Somerville joined Cambridge and the MWRA in submitting an updated draft overflow control plan on May 1, 2026.

The free lead line program has ended; your address may still matter

In 2019 Somerville counted 449 known lead service lines, 3.6% of all lines in the city, and began replacing them from the main into the home at no charge to owners, moving on to other non-copper lines after the lead. Crews replaced 69 lines in 2021, 102 in 2022 and 76 in 2023 and 2024, and a fourth phase wrapped up in 2025, when the city announced that the program had concluded.

The city hasn't published a count of lead lines left after 2025, so it's worth checking rather than assuming. Its Service Line Inventory spreadsheet, dated July 2025, is searchable by address, and questions go to (617) 625-6600 ext. 5400 or [email protected]. If your line shows as lead or unknown, a plumber can look at the exposed pipe next to the meter, and the lead pipe guide on this site covers private replacement now that the city program is over.

Backflow devices, frozen pipes and who to call

Installing an RPZ or double-check backflow device in Somerville takes a permit from the Water Superintendent. The fee on the city's current page is $90, doubled to $180 if the device is installed before the permit is issued. An inspection has to be scheduled within 14 days of installation, and the water won't be turned on until the device passes its test, so build that into the plumber's schedule.

For frozen pipes, Somerville's guidance is to call a licensed plumber first to find out whether the problem is inside the property; the same page lists 311 (617-666-3311) as the city's 24-hour customer service line. Our frozen pipes page covers what to do while you wait.