Why does a pipe split when it freezes?
Water expands by roughly a tenth in volume as it freezes. In a sealed pipe the ice pushes outward, and when the pressure exceeds what the pipe or joint can hold, it splits. The split may open only when the ice has melted and the pressure is released.
The pipe is most at risk where ice forms in a section that is closed at both ends, such as a dead leg between a valve and a closed faucet. Water in that section has nowhere to go as it expands, so the pressure builds. A pipe that is open at a faucet can release some of the pressure, which is why a slow drip is sometimes recommended in very cold spells.
Copper, plastic and galvanized pipe all split under this pressure, but they split in different ways. Copper often splits along a seam or at a joint, plastic can crack along its length, and older galvanized pipe may already be thin inside. The crew identifies the material of the split because it affects how the repair is made.
Where in a house do frozen pipes usually fail?
Frozen pipes usually fail where they are cold and closed off: in an outside wall with cold air behind it, under a floor with no insulation, in a crawl space, or in a garage or cellar corner near a door. The place of the break is often far from the place where the water shows up.
The water follows the framing. A split in an exterior wall can run down the stud cavity, across a sill plate and out at a floor register two rooms away. A split in a crawl space can soak the insulation and wet the joists under the living room. The stain on the ceiling is therefore the least reliable clue to where the break is.
A house with a crawl space or a cellar has a further complication. Water in the crawl space can sit against the underside of the floor for a long time, and it may not be seen until a floor softens or a cupboard base begins to lift. The crew checks the underside of the floor whenever a split is in or near the floor line.
What should I do when I find water and the faucets are dry?
Shut the main at the house first, then open the faucets to drain the lines, then call. Do not light a flame or use a heat gun on a pipe you cannot see, because the heat can start a fire in insulation or framing and can drive water deeper into the wall.
If you can reach a frozen section that is exposed, such as a pipe under a sink or in a cabinet, warm air from a hair dryer or a space heater placed at a safe distance is a reasonable step. Keep the heat moving, keep it away from wood and insulation, and stop as soon as water begins to run, because a thawed pipe that has split will then leak.
Do not try to thaw a pipe inside a wall. The heat cannot be controlled there, and the water that comes out will go into the wall rather than the drain. Call the line, tell the technician where you think the pipe runs and how cold that wall is, and leave the wall alone until the crew has seen it.
Who repairs the pipe, and who dries the house?
The repair to the pipe is made by a plumber. The drying and removal of wet materials is done by the restoration crew. The two jobs happen in sequence, because the house cannot be dried properly while the leak is still running, and the repair cannot be finished while the house is still wet.
The crew shuts the water, finds the break, and tells you who needs to repair it. A plumber is asked for the credentials the job requires, and you should ask for them on the phone or when the plumber calls to arrange the visit. The restoration crew does not carry out pipe repairs itself.
Once the plumber has finished, the crew checks the repaired line for leaks, reads the moisture in the area and then dries the house. A plumbing repair that is made before the house is dry is usually a repair that will have to be opened again, so the sequence matters for the cost as well as the result.
How do I stop it happening again?
Keep cold air away from the pipe, insulate the exposed sections, and keep the house warm enough that the water inside does not freeze. Shut the main and drain the line when you leave the house empty for a long period in cold weather, because an empty house can freeze before anyone is there to notice.
Pipe insulation, heat tape and closing gaps in the wall, floor and crawl space all reduce the risk. Heat tape must be installed and used according to its maker's instructions, because a faulty tape or one that is damaged is itself a fire risk. Tell the plumber which sections are in the coldest places so that they are protected first.
Watch for the early signs. A cold spot on a wall, a slow drip at a faucet, or a drop in flow at one fixture is often a sign that a line is partly frozen. Open the faucet, keep it running slowly and call a plumber before the line splits, if the house is occupied and the cold is persistent.
