How to Keep Pipes From Freezing in a Boston House (Including the Ones Everyone Forgets)

Frozen pipes are the most expensive water damage call of the winter, because they burst while nobody is home and run for hours. The fixes are cheap and most of them take an afternoon.

Where pipes actually freeze

Not in the middle of the house. They freeze where they run along exterior walls, through unheated spaces, or near gaps that let cold air in: kitchen sinks on outside walls, bathrooms above garages, pipes in crawlspaces and attics, the line to the outdoor faucet, and anything in a porch or mudroom addition that was never insulated properly. In older Boston homes, the first-floor bath that was added into what used to be a back porch is the usual suspect.

Before the first freeze

• Insulate exposed pipes in the basement, crawlspace, and garage with foam sleeves. Ten dollars a run.
• Seal gaps where pipes enter the house, and any daylight you can see around the sill plate. Cold air on a pipe freezes it faster than cold air in a room.
• Shut off and drain outdoor faucets from the inside valve.
• Open the cabinet doors under sinks on exterior walls during cold snaps so room heat reaches the pipes.
• Know where your main shutoff is and make sure it turns.

During a deep freeze

When it drops into the single digits, let the faucet farthest from the main drip a thin stream. Moving water does not freeze as easily, and it relieves the pressure that actually bursts the pipe. Keep the thermostat at 55 or above even if you are away; the cost of heat for a week is nothing next to a rebuild.

If you are leaving for more than a few days

Shut off the main and open the lowest faucet to drain the lines. Or, if that is not practical, have someone check the house every two days. A burst pipe in an empty house in January runs until someone notices, and we have seen that mean ten thousand gallons through three floors.

If a pipe freezes but has not burst

Open the faucet it feeds, then warm the pipe slowly with a hair dryer or warm towels, starting from the faucet end. Never use a torch or open flame. If you cannot find the frozen spot or the pipe is inside a wall, call a plumber before it thaws, because the split often does not show until the ice lets go.

If it bursts

Main shutoff first, then photos, then call us. Frozen-pipe damage is covered by almost every policy as long as you kept the heat on, and the faster drying starts, the smaller the claim.