Why Summer Storms Back Up Boston Sewers (and How to Stay Ahead of It)

Published August 5, 2026 · Snake-It-Away Inc.

If your drains gurgle or your basement floor drain backs up every time there is a heavy summer downpour, it is not a coincidence. Storms put older sewer systems under real stress, and in the Boston area that shows up as backups. Here is why it happens and what you can do about it.

Why rain causes a sewer backup

A few things stack up during a storm:

• Older, combined sewer areas. Parts of Boston and the older suburbs still run on systems where storm runoff and household sewage share the same pipes. A big rain overwhelms the line, and water backs up toward the lowest drain in your house.
• A line already narrowed by roots or grease. If your sewer line is half-blocked by root intrusion or years of buildup, it flows fine on a dry day but cannot handle the surge when a storm pushes through. The rain just exposes a problem that was already there.
• Groundwater seeping into cracked pipe. Heavy rain raises the water table, and a cracked or offset sewer line lets that extra water in, filling the pipe from the outside.

The warning signs

• The backup happens during or right after heavy rain
• Water comes up through the lowest drain (usually a basement floor drain)
• Multiple fixtures gurgle or drain slowly at once

That pattern points to the main line, not a single clogged fixture.

How to get ahead of it

• Get the line looked at before the next storm. A camera inspection shows whether roots, buildup, or a cracked pipe is the real weak point, so you fix the cause instead of mopping up after every rain.
• Clear a line that is already partly blocked. If roots or grease have narrowed the pipe, root removal or hydro jetting restores the full capacity you need when a storm hits.
• Fix a damaged line. If groundwater is getting in through a break, the real answer is a sewer line repair.

When it's backing up right now

If sewage is actively rising, stop running water and call, that is what our 24/7 emergency service is for. Our guide on what to do when your main line backs up walks through the steps. Call Snake It Away at (781) 858-8314. Medford-based, family-owned since 1997, serving the Boston metro.