Preventing frozen pipes on Long Island
The pipe does not usually burst while frozen. It bursts when it thaws — which is why the damage is discovered by the sound of running water.
- Exterior walls, unheated spaces and crawl spaces first
- Pressure between the ice and the closed tap causes the split
- Damage appears on thawing, often while nobody is home
- Prevention is cheap; the loss rarely is
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Why frozen pipes burst
The common explanation — that ice expands and splits the pipe — is only half right. What usually causes the failure is pressure.
As ice forms it blocks the pipe. Water continues to be pushed against that blockage from the supply side, and the pressure builds in the section between the ice plug and the nearest closed tap. That trapped pressure is what splits the pipe, and the split frequently occurs some distance from the ice itself.
Then, while frozen, nothing leaks — the ice is plugging its own hole. The water arrives when it thaws, which is typically hours or days later, and frequently when nobody is in the building.
Which pipes are at risk
- Pipes in exterior walls, particularly on the north side
- Unheated spaces: crawl spaces, attics, garages, basements without heat
- Outdoor taps and the pipe feeding them
- Irrigation lines and pool supply
- Anything in a space where the heating has failed or been turned off
- Kitchen and bathroom supplies inside cabinets against an exterior wall
That last one catches people out. A cabinet door keeps heated room air away from the pipes behind it, so the coldest point in a warm kitchen is often under the sink.
Prevention, cheapest first
Open cabinet doors under sinks on exterior walls during a cold snap. Free, and it works.
Let a tap drip on the most vulnerable run. Moving water freezes less readily, and more importantly an open tap relieves the pressure that causes the split. A slow drip costs pennies.
Keep the heat on throughout the house, including rooms you do not use. Do not shut heating off in a spare bedroom on an exterior wall.
Disconnect and drain outdoor hoses before the first freeze, and shut off and drain the outdoor tap supply if it has an interior valve.
Blow out the irrigation system in autumn. This is standard practice out here and skipping it is a predictable, expensive mistake.
Insulate exposed pipes in crawl spaces, attics and garages with foam sleeves. Inexpensive and straightforward.
Seal draughts where cold air reaches pipes — rim joists, foundation vents, gaps around service entries. A cold draught blowing directly on a pipe defeats insulation.
Heat tape on genuinely vulnerable runs that cannot be insulated adequately. Use a product intended for the purpose and follow the instructions; improvised heating on pipework is a fire risk.
If you are leaving the house
For a few days: keep the heat at 55°F or above, not off. Leave interior doors open so warm air circulates. Ask someone to check the property.
For an extended absence or a seasonal closure: shut the water off at the main and drain the lines. That single step removes the risk almost entirely, because a pipe with no water in it cannot burst and a closed main cannot feed a failure.
This matters most on the East End and Fire Island, where houses stand empty from autumn to spring and a January failure runs undetected until spring.
If a pipe is frozen but has not burst
You will know because a tap gives little or nothing while others run normally.
Open the tap that pipe feeds, so melting water has somewhere to go and pressure can relieve.
Warm it gently along the run — a hairdryer, a heating pad, towels soaked in hot water. Start nearest the tap and work back toward the frozen section.
Never use an open flame. Blowtorches on pipework start house fires, and they are a leading cause of them during cold snaps.
Know where the main is and be ready. If the pipe has already split, water arrives the moment the ice clears, and the difference between two minutes and twenty is substantial.
If you cannot locate or reach the frozen section, or the thaw produces water, shut the main off and call a plumber.
Questions, answered
Does dripping a tap really help?
Yes, for two reasons. Moving water is less likely to freeze, and more importantly an open tap gives the pressure somewhere to go — since the split is caused by pressure building between an ice plug and a closed tap, an open one relieves it. It is one of the cheapest preventions available.
Is frozen pipe damage covered by insurance?
Generally yes, as sudden and accidental damage — but often only if you took reasonable steps. Many policies exclude damage in an unoccupied property where heat was not maintained or the system was not drained. Leaving a seasonal house unheated with the water on is the scenario carriers are explicitly excluding.
How cold does it have to get?
There is no single number, because it depends on exposure, insulation, wind and how long the cold lasts. Pipes in unheated or exposed locations can freeze in sustained temperatures around 20°F, and wind on a draughty crawl space accelerates it considerably. Duration matters as much as the low.
What if it bursts while we're away?
Water runs until someone stops it, which is why the prevention advice is so heavily weighted toward closing the main when you leave. A monitored leak detector with cellular alerting, and ideally an automatic shutoff valve, is the difference between a room and a rebuild on an unoccupied property.
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Pipe burst after a freeze?
Shut the main off first, then call. If it thawed while you were away, tell us how long — it changes what we bring.
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