Why Boston Basements Flood in the Same Storm That Knocks the Power Out (and the $400 Fix)

The storms that flood basements around Boston are the same storms that take the power down. A sump pump with no battery backup stops at the exact moment it is needed most. Here is what a backup does, what it costs, and how to know if yours is working.

The sequence we see every spring and fall

A nor'easter drops three inches of rain overnight. Groundwater rises, the sump pit fills, the pump runs. Then a limb takes down a line, the power goes out, and the pump stops. Four hours later there is two inches of water across the basement floor. By the time the owner wakes up, the finished walls have been wicking water for most of the night.

The pump was fine. The power was the problem. We get a run of these calls after every big storm in Quincy, Weymouth, and Dorchester, and almost none of those houses had a backup.

What a battery backup actually is

A second, smaller pump that sits in the same pit, wired to a deep-cycle battery and a charger. When the main pump loses power or fails, the float on the backup takes over. A good unit runs for six to twelve hours of steady pumping on one charge, which covers almost every outage we see in Greater Boston. Installed cost with a decent battery is usually $400 to $900 depending on the pump.

Water-powered backups

If the house has municipal water, a water-powered backup uses city water pressure to pull water out of the pit, no battery at all. It runs as long as the water main is up. The tradeoff is that it uses roughly one gallon of city water for every two it pumps out, so a long storm shows up on the water bill. For a house that loses power often, it is the more reliable choice.

How to test what you have

• Unplug the main pump and pour a bucket of water into the pit. The backup should start on its own.
• Check the battery date. Most are good for three to five years and die quietly.
• Make sure the discharge pipe goes outside and away from the foundation, not into a floor drain that backs up in the same storm.
• Listen to the main pump. Grinding or hesitating means it is close to failing, and no backup should be covering for a dying primary.

If it already flooded

Get the water out within 24 hours, pull anything wet off the floor, and call us before you start cutting drywall. Groundwater is Category 2 or 3 water, which changes what can be dried and what has to be replaced. We extract, set drying equipment, and document it for your claim, and we will tell you straight whether the finished walls can be saved.