Frozen pipes: the winter checklist for pre-war apartments

Every January we thaw and repair a few dozen frozen pipes, mostly in the same kinds of apartments: pre-war walk-ups with plumbing in an exterior wall and a heating system that was balanced for a building that no longer exists. Here is the checklist we hand out in November.

Before the first freeze

Find the pipes that run along outside walls — usually the kitchen sink and any bathroom on a corner. Open the cabinet doors under them on cold nights so room air reaches the pipe. If a radiator under a window has been cold for a winter or two, get it bled or balanced now; an unheated room is where the pipe in the wall freezes.

During a cold snap

Leave a faucet on the exterior wall dripping — a pencil-thin stream is enough. Keep the heat on when you travel, no lower than 55°F. If you go away for more than a weekend, shut the supply valve at the apartment and open the faucets to drain what you can.

If a pipe has frozen

Turn off the water at the shut-off. Open the faucet so melting water has somewhere to go. Warm the pipe slowly — a hair dryer, warm towels, never an open flame. If you see a split in the pipe or water anywhere it should not be, stop and call; that is the $349 thaw-and-repair on the board and it is cheaper at 9 AM than at 2 AM.

We also fit insulation on exposed runs and replace shut-off valves that no longer close — $249 for a new shut-off, and it is the most useful $249 in a pre-war building.