What to Do When Your Pipes Freeze
Step-by-step guide for what to do when residential pipes freeze in Massachusetts winters. How to thaw safely, what NEVER to do, and when to call a plumber immediately.
Frozen pipes are a New England winter inevitability for any home that loses heat during a cold snap. The danger isn't the frozen pipe itself — it's the burst that often follows when frozen water expands and splits the pipe. Once frozen pipes thaw with a split, you have a major water leak in minutes. Here's exactly what to do when you discover a frozen pipe in a Greater Boston home, in order.
Step 1: Turn off the main water supply
This is the first move every time. The main shutoff is usually in the basement, near where the water line enters the house from the street. Turn it fully off. This won't unfreeze the pipe, but if the pipe has already split (and you may not be able to see this yet), it limits the damage when the ice thaws and water starts flowing through the split. If you don't know where your main shutoff is, find it now before you ever need it.
Step 2: Open faucets fed by the frozen pipe
Turn on the faucet at the end of the affected line — both hot and cold sides if you're not sure which is frozen. This relieves pressure as the ice thaws and gives water somewhere to go that isn't your wall.
Step 3: Identify the frozen section
Most freezes happen in pipes that run through unheated spaces — exterior walls, crawl spaces, attics, garages, or basements that lost heat. Trace the line from the cold-affected faucet back toward the supply until you find the frozen section. It usually feels noticeably colder than the rest of the pipe and may have visible frost on it.
Step 4: Apply gentle heat to the frozen section
Use a hair dryer, heat lamp, electric heat tape, or towels soaked in hot water. Start at the faucet end of the frozen section and work toward the supply — this lets melted water flow out as you progress. Be patient — this can take 30-60 minutes per section.
Step 5: NEVER use open flames
No propane torch. No blowtorch. No charcoal heater. Open flames can melt PEX, ignite framing inside walls, and cause house fires. We see fire damage from this every winter. Stick to dry heat (hair dryer) or warm water.
Step 6: Check for leaks as the pipe thaws
As ice melts, water starts moving through the pipe again. If the pipe split while frozen, you'll see leaks now. If you see ANY leak, turn off the water immediately and call a plumber. Don't try to patch a split pipe yourself in freezing conditions — get a professional repair.
Step 7: After it's thawed, prevent the next freeze
Insulate the pipe with foam pipe sleeves (cheap, easy, $20 at the hardware store). For pipes in really cold spaces, add heat tape with a thermostat that kicks on around 35°F. For pipes in exterior walls, the longer-term fix is interior insulation work.
When to skip all this and just call us
If you can't find the frozen section, can't access it safely, or see any signs of a leak as it thaws, call us at (781) 879-2922. Same goes if multiple pipes are frozen (suggesting a bigger heating problem in part of the house) or if your heating system itself failed. We do emergency calls year-round and freeze-related calls are common in January and February.
Frequently Asked Questions
At what temperature do pipes freeze?
Generally below 20°F sustained, though pipes in poorly insulated walls can freeze higher (around 32°F) if exposed to direct wind. Most freeze damage in Greater Boston happens during the multi-day cold snaps when temps stay below 10°F.
How do I know if a frozen pipe burst?
Often you won't know until it thaws and water starts coming out. Sometimes you'll hear a loud bang when the ice expands and splits the pipe. Most common sign is no water flow from one fixture, then sudden flow plus a leak when temps warm up.
Can I prevent frozen pipes during a cold snap?
Yes: keep the heat on at least 55°F even if you're away, open cabinet doors under sinks on exterior walls to let warm air circulate, let a thin trickle of water run from the highest-risk faucet, and insulate any exposed pipe runs in crawl spaces or attics ahead of time.
My pipes froze but didn't burst — am I in the clear?
Sometimes yes. But a pipe that freezes once tends to freeze again at the same spot, and each cycle weakens the pipe. Fix the insulation or heat-tape the run before next winter.
Do you do emergency calls for burst pipes?
Yes — especially for Billerica, Woburn, Winchester, Lexington, and Stoneham customers. Call (781) 879-2922.
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