Frozen pipes do not usually burst where the ice forms. Ice expands and blocks the pipe, pressure builds between that blockage and a closed faucet downstream, and the pipe fails at the weak point in that pressurized section. That is why the damage often appears somewhere you were not worried about.
The work below takes an afternoon, costs very little, and addresses most of what actually goes wrong. Do it in early autumn rather than on the night of the first hard freeze warning, when hardware stores are out of pipe insulation and plumbers are not answering.
Outside the House
Disconnect every hose. A hose left attached traps water in the bib and in the pipe behind it. This is the single most common cause of a burst line at the exterior wall, and it is entirely preventable.
Shut off and drain hose bibs. Find the interior shutoff for each exterior faucet, close it, then open the outside faucet to let the section drain. If you have frost proof bibs, the valve seat sits inside the heated wall and they mostly take care of themselves, but they still need the hose off to drain properly.
Blow out the irrigation system. In freezing climates this generally means compressed air, and it is worth having done professionally if you do not have the right compressor. Backflow preventers are expensive and they crack readily.
Drain and shut off any outdoor kitchen, pool line, or exterior shower.
Check the sump discharge line. A discharge line that freezes leaves the pump running against a blockage, which burns out the motor and floods the basement. Confirm it slopes away, is not buried in a low spot that collects water, and terminates somewhere that will not ice over. More on this in sump pumps, backups, and basement water.
The Vulnerable Interior Spots
Not all pipe is equally at risk. The failures cluster in predictable places.
- Unheated spaces. Crawl spaces, attics, garages, and unfinished basements
- Exterior walls, especially where a kitchen or bathroom sink sits on an outside wall
- Cantilevered floors, meaning a bathroom or bay that overhangs, where the floor cavity is open to outside air
- Near a foundation vent or any air path into a crawl space
- Garage plumbing, particularly a laundry hookup or utility sink
Insulate exposed pipe in those areas with foam sleeves, which are inexpensive and take minutes per run. Where a run is genuinely exposed to freezing air, self regulating heat cable is the more reliable answer, installed per the manufacturer's instructions.
Air sealing matters as much as insulation. A pipe in an insulated wall that has cold air blowing across it through an unsealed penetration will freeze anyway. Sealing the air path is often the actual fix, which is a theme covered more broadly in attic insulation and air sealing before winter.
Before You Leave for a Trip
Extended absences in winter are when the expensive failures happen, because nobody is there to notice for a week.
- Do not set the thermostat below about 55 degrees. The savings are small and the risk is not.
- Open cabinet doors under sinks on exterior walls so room air reaches the pipes.
- Consider shutting off the main and draining the system if you will be gone a long time and the house has a drainable layout.
- Have someone check the house, ideally every few days. A smart thermostat with a low temperature alert and a water leak sensor with a phone notification cover much of this cheaply.
During a Cold Snap
Let a faucet drip. A slow drip on the fixture farthest from where water enters the house keeps water moving through the vulnerable run and relieves pressure. Use the cold side, or both on a mixing faucet.
Open cabinets under exposed sinks.
Keep the garage door closed if there is plumbing in the garage.
Know where the main shutoff is and keep the path to it clear. If a pipe does burst, the seconds between discovering it and closing that valve determine most of the damage.
If a Pipe Freezes but Has Not Burst
You will notice it as no flow or a trickle at one fixture while others work normally.
- Open the faucet served by the frozen line, so melting water has somewhere to go and pressure can release.
- Apply gentle heat to the suspected section, working from the faucet end back toward the blockage. A hair dryer, a heating pad, or towels soaked in hot water all work.
- Never use an open flame, a propane torch, or a kerosene heater on a pipe. This causes house fires every winter.
- If you cannot locate or reach it, or if the frozen run is inside a wall, call a plumber before it thaws on its own.
If a pipe has already burst, shut the main first and then call. Then read what homeowners insurance covers when a pipe leaks before you start cleaning up, because what you photograph in the first ten minutes matters.
Septic and Well Systems
Septic systems freeze less often than people expect, but they do. Keep traffic off the drain field, since compacted snow loses its insulating value. Leave grass cover in place rather than mowing it short in late autumn. Fix any dripping fixture, because a slow trickle of cold water into the tank is a freeze risk.
Well systems need the pressure tank and any above ground piping protected, and well houses need to stay above freezing.
What to Have a Plumber Do
Most of the list above is homeowner work. The items worth paying for are irrigation blowouts if you lack a compressor, heat cable installation on a long or awkward run, insulating pipe in a crawl space you would rather not spend an afternoon in, and any repair to a bib or valve that is already leaking.
Book it in early autumn. The same scheduling pressure that hits heating contractors hits plumbers, and it hits them all at once on the first cold weekend. The broader seasonal walkthrough is in the fall exterior maintenance checklist.
If you want quotes for plumbing work before winter, tell us about your home and we will connect you with plumbers serving your area. It is free to use, with no obligation to hire.