A frozen pipe often splits while it is still frozen and leaks only once it thaws. After a thaw, shut the water off at the house, check the lines for a split, photograph the break, and call the utility if the freeze is on its side of the meter. Do not turn the water on to test it until the line has been checked.
Key takeaways
- A pipe splits when water inside it expands as it freezes, but the leak often starts only when the ice melts and the water moves again.
- The first step after a thaw is to shut the water off at the house and open the faucets to drain the lines.
- A split line is found by checking the faucets, the pressure and the wet areas, then opening the smallest access that shows the break.
- Photograph the break and the water path before anything is moved, because the record is what the plumber and the insurer will use.
- If the freeze is on the utility side of the meter, the utility repairs it, and the house side is the owner's to repair through a plumber.
Why does a frozen pipe leak days after the cold?
The water inside a frozen pipe expands, and the pressure can split the pipe or a joint. The ice often holds the split closed until the pipe warms, so the leak begins when the water starts to move again, which can be hours or days later.
Water expands as it turns to ice, and in a closed section of pipe that expansion pushes outward. Where the pipe or a fitting cannot hold the pressure, it cracks or pulls apart. The ice plugs the crack for as long as the pipe stays frozen, so nothing is seen while the cold lasts.
When the thaw comes, the ice melts from the outside in and the water begins to move. The split then leaks into the wall, the floor or the crawl space. That is why the first sign can come during a warm spell, a shower or when a faucet is opened, rather than during the freeze.
A line that froze hard can split at a joint, a fitting or a bend rather than along its length. Those weak points are where the break is most often found, and they are also where the pressure builds first, which is one reason the crew checks the fittings before it checks the run of pipe.
What do I do first when I find the water?
Shut the main shut-off at the house, open the faucets on the lowest floor so the lines drain, and keep them open until the line has been checked. This stops more water entering the wall while you arrange the next step.
The main shut-off is often in the cellar or near the point where the service comes into the house, but it is not always easy to find. If you cannot find it, call the utility or a plumber and say where the water is. Do not operate the curb stop or any valve outside the house yourself.
Keep the faucets open while you work, and do not turn the water back on to see whether the leak has stopped. A split line that is pressurised will leak again as soon as it is filled, and the water will run further into the building before you can shut it.
How do I tell where the break is?
Check the faucets for flow, look for the wettest area, and notice whether the water seems to come from one wall or from the floor below. A break on the supply side often shows as wet ground or a wet wall, and the path of the water is more useful than the first stain.
Open the faucets one at a time after the main is closed, and note which ones run and which do not. A line that is frozen will not run at all at the faucet, while a line that has split may run briefly and then stop once the pressure drops.
Trace the wet areas to see where the water is coming from and where it went. A crew can read the wall with a moisture meter and open a small access point where the reading is highest. The break is then confirmed, photographed and recorded before any repair is made.
Where the break is inside a wall, the water often shows first at a floor line, a baseboard or a light switch some distance from the pipe. A break in an upstairs wall can run down through the framing and surface in a cellar corner, so the search should start at the point the water reaches the building, not at the spot where the stain is biggest.
Should I thaw the pipe with heat?
You can warm an exposed section that you can see, using a hair dryer or a space heater placed at a safe distance, while the faucets are open and you watch the line. Do not use an open flame, a propane torch or a heat gun near a pipe inside a wall or near insulation.
Warm the pipe slowly and stop as soon as the water runs, because a split pipe will leak once it thaws. Keep the heat moving and away from wood, insulation and cloth. Heat that is applied to a pipe inside a wall cannot be controlled, and it can start a fire in the framing.
Heat tape, if fitted, must be used according to its maker's instructions, because a damaged or faulty tape is itself a fire risk. Do not install or repair heat tape without checking the instructions, and ask a plumber to look at any tape that is old or damaged.
When is the freeze the utility's responsibility?
Where the frozen section is on the utility's side of the meter, the utility repairs it. The meter is the usual dividing point, but the arrangement depends on the service and the property, so check your own account to see where the utility's responsibility ends.
A frozen service line between the street and the meter is a question for the utility, and the owner should call the utility on its own line and say where the water is. A meter that keeps turning with the house shut off points outside the house, and that is the first clue to the utility side.
The house side of the meter is the owner's to repair, through a plumber. A frozen line inside the house that has split is therefore an owner's repair, even when the crew is the first to arrive, and the crew records which side the break is on so the right trade is called.
A utility that finds the break on its side will usually want to know the time you first saw the water and whether the meter was turning. Those two details, together with a photograph of the meter, help the utility plan its repair and set a clear record for the house side as well.
What should I photograph and keep?
Photograph the break, the water line on the floor and walls, the meter and the faucets, and keep the photographs with the date. Keep any part of the pipe that has split, because it shows how the failure happened and the insurer may want to see it.
Take the photographs before anything is moved. A photograph of a wet floor after the furniture is moved is less useful than one of the furniture in place. Note the time the water was first seen and the time the house was shut off.
Keep the plumber's written scope and the invoice for the repair, and keep the crew's written record of the readings. Together they show the cause, the path and the work done, which is the record the insurer will ask for.
A plumber's invoice should describe the section of pipe repaired, the material used and the work done on any fitting. Keep the old section if it is still available, because the failure pattern can show whether the cold, the age of the pipe or a joint caused the break.
An empty house needs its own plan in cold weather. Shut the main, drain the lines, and set the heat to a level that keeps the rooms above freezing, because a house that is left unheated for several days can freeze before anyone is there to notice. A neighbour or a caretaker who can look at the house and the thermostat is worth arranging in advance.
How do I stop it happening again?
Keep cold air away from exposed pipes, insulate the sections that are in the coldest places, and keep the house warm enough that the water inside does not freeze. When you leave the house empty in cold weather, shut the main and drain the lines.
Look at the pipes in exterior walls, crawl spaces and unheated spaces, and insulate or protect any section that is exposed. Close gaps that let cold air blow across the pipe, and check the crawl space vents and hatch for draughts.
Ask a plumber which sections are most at risk in your house and whether a drip at a faucet or a heating cable would help in those places. Those are the sections to protect first, and the plumber can advise on the arrangement for your house.
Frequently asked questions
Can I just run the water to see if the pipe is still frozen?
Not until the line has been checked. A split pipe leaks into the building once water is turned on, so the line should be checked for a break before the water is run.
The water came back on but now it leaks at the wall. What now?
Shut the main again and open the faucets to drain the line. Call a plumber to repair the break, and call the restoration line to dry the wall and the floor.
Who pays for the repair of a frozen pipe?
The utility pays for its side of the meter, and the owner pays for the house side. Whether a policy covers the damage is decided by the policy and the insurer.
Should I leave the faucets dripping during a cold spell?
A slow drip on the exposed section can keep the water moving and reduce the pressure that builds in a closed line. It is a precaution and is not a substitute for insulating or heating the pipe.
How do I know if a pipe is frozen and not just empty?
A frozen line usually shows no flow at the faucet while the others run, and the section may feel cold or show frost. Check the other faucets and the pressure before deciding, and call a plumber if you are not sure.
Can a pipe that has thawed still be split?
Yes. A split can be closed by ice and stay closed while the pipe is frozen, and it may open only once the water moves again. A line that has thawed and seems to run normally should still be checked, because a split can leak slowly into the framing for some time before a stain appears.
What if the house was empty when the pipe froze?
Shut the main, drain the lines and check the house as soon as you can get there, without turning the water on first. Look for the wet areas, the frost and any stain, and call the line with what you find. The crew will need to know that the house was empty, because that changes how long the water may have run.
This guide is general information for Anchorage Municipality homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.