Here is something most people get backward about winter plumbing. A pipe rarely splits at the spot where the ice forms. Water expands by roughly nine percent as it freezes, and once a plug of ice seals off a section of line, the water trapped between that plug and a closed faucet has nowhere to go. Pressure builds in that stretch until the weakest point gives, sometimes several feet away from the ice. That is why a burst so often shows up somewhere unexpected, behind a finished wall or above a ceiling, and why it usually announces itself only once things start to thaw.
Calls like that tend to arrive in clusters, often before sunrise on the first morning after a hard freeze. A plumber in Lyons running trucks around the clock out of the village, with separate lines for Chicago and the suburbs, ends up seeing the whole progression every January, from frosted hose bibs in late fall to split copper in finished basements after a deep cold snap. What follows is that progression, laid out by temperature, so you know which part of the house to worry about as the forecast drops.
Forty Degrees and Falling
The cheapest protection happens before the first frost. Outdoor faucets are the classic first casualty, and the fix is simple. Disconnect every garden hose, because a hose left attached holds water inside the faucet body and defeats even a frost free sillcock. If your home has older outdoor faucets, look for a shutoff valve on the inside wall, close it, then open the outside tap to drain what is left.
This is also the season to walk the basement and crawlspace with a flashlight. Look for pipes running along the rim joist, the band of framing that sits right on top of the foundation, since that area gets far colder than the middle of the room. Foam pipe sleeves cost very little and slip on in minutes. Seal gaps where cables or dryer vents pass through the wall, and replace any cracked basement window panes. A pencil sized draft can freeze a pipe even in a heated basement.
Finally, find your main water shutoff and make sure it actually turns. Old gate valves seize after years of sitting still, and the middle of a flood is a bad time to learn that yours won’t budge.
The Low Twenties, When Weak Spots Show Themselves
Most homes sail through the first few freezing nights. The trouble usually starts when overnight lows settle into the low twenties and stay there. That is when pipes in unheated or poorly insulated parts of the house start losing heat faster than the surrounding air can replace it.
In older Chicagoland homes, these are usually the first spots to go.
- Kitchen sink lines on exterior walls, especially behind closed cabinets.
- Supply pipes running through an attached garage or an enclosed back porch.
- Lines near the water meter in a cold front corner of the basement.
- Bathroom plumbing in a rear addition built over a crawlspace rather than full basement.
- Any pipe that has frozen before, since whatever caused it the first time is probably still there.
If you know your home has one of these trouble spots, this is the temperature range to start paying attention.
Single Digits and the Case for a Dripping Faucet
Once the forecast drops into single digits, active prevention matters. Open the cabinet doors under sinks on outside walls so warm room air can reach the pipes. Keep the thermostat steady day and night instead of setting it back while you sleep, since the coldest hours are exactly when a setback leaves pipes exposed.
Letting a faucet drip feels wasteful, but it works for two reasons. Moving water is harder to freeze, and an open tap relieves the pressure that actually causes the split. The City of Chicago’s water department recommends running a thin stream of cold water on each floor at the fixtures farthest from where the main enters the house, and its one page freeze prevention sheet is worth taping inside a utility closet. Keep the garage door closed, and if you plan to travel, leave the heat on and ask someone to check the house.
Below Zero, When the Tap Goes Dry
During the worst recent cold snaps, when O’Hare readings have fallen past twenty below, plumbers across the area have spent days doing nothing but thawing lines. The first sign is usually a faucet that gives a trickle or nothing at all while the rest of the house works normally.
If that happens, leave the faucet open so melting water has somewhere to go. Then work out where the frozen section probably is, usually along an outside wall or in an unheated pocket, and warm it gently with a hair dryer, a heating pad or towels soaked in hot water. Start near the faucet and move toward the cold section. Never use a torch, a candle or any open flame. Old framing and insulation catch fire easily, and overheating a pipe can damage it as surely as the ice. If you can’t reach the frozen section or nothing changes after a reasonable effort, that is the point to bring in someone with proper thawing equipment.
When the Pipe Gives Way Anyway
Sometimes the warning signs get missed, and the first clue is water coming through a ceiling. Moving quickly in the first few minutes makes a big difference in how much gets ruined.
- Shut off the main water valve immediately.
- Turn off electricity to any area where water is near outlets, fixtures or appliances, but only if you can reach the panel without standing in water.
- Open the lowest faucets in the house to drain water still sitting in the lines.
- Move furniture, rugs and stored boxes out of the wet area.
- Photograph the damage and the broken section of pipe before any cleanup begins.
Making Next Winter Easier
A burst is more than a pipe to repair. It shows you exactly where the house is losing heat. After the repair, ask whether the line can be rerouted away from the exterior wall or better insulated where it runs, because a pipe that froze once will very likely freeze again if nothing changes around it. Thermostatically controlled heat cable can protect a stubborn section that can’t be moved.
Newer tools help too. Inexpensive water sensors placed under sinks and near the water heater send an alert to your phone the moment they get wet, and automatic shutoff valves installed on the main can close the supply on their own when they detect a leak. For anyone who travels in winter or rents out a two flat, that can mean a damp floor instead of a gutted basement.
It also pays to read your homeowners policy before the cold arrives. Sudden pipe bursts are often covered, but many policies exclude damage when a home was left without heat or unattended for long stretches. Knowing that before the cold arrives beats learning it with a wet floor and an adjuster on the phone.
