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How to Prevent Frozen Pipes (Before They Burst and Flood Your House)

The February my neighbor’s kitchen ceiling collapsed onto his breakfast table, I finally took frozen pipes seriously. He had gone to visit his sister for three days over a cold snap — thermostat set to 55, kitchen sink on an exterior wall, no cabinet doors open, no drip. The pipe behind the drywall froze solid, split lengthwise, and when it thawed two days later it ran for almost eight hours before anyone noticed. The insurance adjuster said it was the third one that month.

A burst pipe dumps water at 50 gallons per minute if it is a main supply line. Even a small split on a branch line can flood a room in an hour. And the repair is not just the pipe — it is the drywall, the flooring, the baseboards, sometimes the electrical that runs through the same wall cavity. My neighbor’s bill was $14,000. The pipe itself cost $8.

The good news: preventing frozen pipes is mostly cheap and straightforward. The bad news: most people only do it after the first time they get burned.

Which Pipes Freeze First

Not all pipes are equally at risk. The ones that freeze first are:

What to Do Before Cold Weather Hits

Insulate Exposed Pipes

This is the highest-value prep you can do. Foam pipe insulation sleeves cost about $1 to $3 per 6-foot length at any hardware store. You cut them to size, slip them over the pipe, and tape the seam. It takes five minutes per pipe run.

For pipes you cannot sleeve — too close to the wall, too many bends — use fiberglass pipe wrap. It is messier but conforms to any shape.

Pay attention to joints and valves. Water does not just freeze in straight runs. It freezes at elbows, tees, and valves first, because turbulence there lets ice crystals form more easily.

Install Heat Tape on the Worst Spots

Heat tape (also called heat cable or heat trace) is an electrical wire you wrap along or tape to a pipe. When the temperature drops, a built-in thermostat turns it on and keeps the pipe above freezing. It draws about 3 to 7 watts per foot.

Use it on pipes that insulation alone cannot protect — the hose bib feed line, pipes in a crawlspace with no ambient heat, or a long run along an exterior wall. Plug it into a GFCI-protected outlet. Do not overlap the tape on itself; it can overheat.

Shut Off and Drain Outdoor Faucets

Before the first freeze, disconnect every garden hose. If the hose bib has a shut-off valve inside the house (many do), close that valve and open the outside faucet to drain it. Leave the outside faucet open all winter. Even a tiny amount of water trapped between the closed faucet and the shut-off valve will freeze and split the pipe.

If you have a frost-proof hose bib (the kind that extends 12 to 18 inches into the house), you still need to disconnect the hose. The long stem only works if the valve inside can drain — and a connected hose holds water in the stem.

Seal Air Leaks Near Pipes

Cold air blowing on a pipe freezes it faster than cold air sitting still. Check for gaps where pipes enter the house, cracks in the foundation near plumbing runs, and any place you can feel a draft near a water line. Spray foam or caulk those gaps. A $5 can of spray foam can save you a $5,000 flood.

What to Do When It Drops Below Freezing

These are the nightly habits that make the difference when the temperature is heading into the low 20s Fahrenheit (about -5 Celsius) or colder.

Let faucets drip. Not a full stream — a slow drip, maybe one drop per second. Moving water is much harder to freeze than still water, and the drip relieves pressure buildup if ice does start to form in the pipe. Run both the hot and cold if the pipes are on an exterior wall. The extra water cost is negligible — maybe 50 cents a night.

Open cabinet doors. Kitchen and bathroom cabinets on exterior walls block warm room air from reaching the pipes behind them. Open those doors before bed on cold nights. If you have small children or pets, move any cleaning supplies out of reach first.

Keep the thermostat steady. Do not set the thermostat back more than 5 degrees at night or when you leave the house. The savings on your heating bill are tiny compared to the cost of a burst pipe. If you are going away for more than a day, set the thermostat to at least 55 F (13 C) and have someone check the house daily.

Run a space heater in vulnerable rooms. If you have a bathroom or kitchen on an exterior wall that gets very cold, a small space heater on low can keep the room warm enough to protect the pipes. Make sure it is on a stable surface, away from water, and never left running unattended while you sleep.

If a Pipe Does Freeze

Do not panic. A frozen pipe has not burst yet — it bursts when the ice expands enough to split the pipe wall, or when pressure builds up between the ice blockage and a closed faucet.

  1. Shut off the main water valve. Do this first. If the pipe has already cracked, you want the water off before it thaws.
  2. Open the faucet the frozen pipe feeds. This gives the melting ice somewhere to go and relieves pressure.
  3. Apply heat to the pipe. A hair dryer on high, a heat gun on low, a heating pad wrapped around the pipe, or towels soaked in hot water. Work from the faucet end back toward the frozen section. Never use an open flame — propane torches on water pipes cause house fires.
  4. Check for leaks as it thaws. Run your hand along the pipe. If you feel a split or see water seeping, the pipe burst while frozen. You will need a repair before turning the water back on.
  5. If you cannot find the frozen section, call a plumber. Frozen pipes inside walls are hard to locate and harder to thaw safely. A plumber can use professional pipe-thawing equipment or open the wall to access the pipe.

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Caution: Never use a blowtorch, propane heater, or any open flame to thaw a pipe. The heat is too concentrated, and the risk of igniting wall framing or insulation is real. Every year, house fires start this way.

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