How to Prevent Frozen Pipes From Bursting

To prevent frozen pipes from bursting, you have to fight two things at once: keep the water from freezing, and give any water that does freeze somewhere to push.

Water freezes at 32 degrees, but a pipe inside a wall does not usually freeze until the air around it hits about 20 degrees.

Get ahead of that line and the fix is cheap and simple. Miss it and you are looking at a flooded floor and an insurance claim.

A burst pipe is one of the most common winter disasters, and whether your policy pays depends on the cause. It helps to know whether insurance covers a burst pipe before one ever freezes.

At what temperature do pipes freeze and burst?

Water freezes at 32 degrees Fahrenheit, but the pipe itself is shielded by walls, insulation, and the heat of your home.

Research by the Building Research Council at the University of Illinois found the real danger point is a temperature alert threshold of 20 degrees.

That is the outdoor temperature at which uninsulated pipes in an unheated space, like an attic, actually begin to freeze.

Below 20 degrees the risk climbs fast, especially if the cold holds for four to six hours or longer overnight.

Pipes can still freeze above 20 degrees when they are exposed to wind. A draft blowing across an uninsulated pipe strips its warmth far faster than still air.

So treat 20 degrees as your action line, and act sooner if wind chill is severe or your pipes have frozen before.

Why frozen pipes burst: it is pressure, not the ice

Here is the part most articles get wrong. The ice inside the pipe does not push outward and crack it. Trapped water pressure does.

As ice forms, it acts like a piston, shoving the liquid water still in the pipe toward a closed faucet at the end of the line.

With nowhere to escape, that column of water builds enormous pressure. Building Research Council testing measured a jump from about 35 psi to over 4,000 psi.

The pipe then splits at the weakest point downstream, often where there is little or no ice, between the blockage and the closed tap.

This single fact explains the whole prevention strategy. Open a faucet and you turn a sealed pipe into a pressure relief valve, so ice has room to expand harmlessly.

It also explains a nasty surprise. Many pipes burst after they thaw, not while frozen.

The ice can seal the crack while it is solid. When it melts, water rushes the split and the flooding starts, sometimes hours or days later.

How to prevent frozen pipes from bursting tonight

When a hard freeze is in the forecast, these are the moves that work in the next few hours, no tools required.

1. Let a faucet drip. Once it drops below 20 degrees, open a tap to a slow, steady trickle of roughly one drip per second.

Drip the cold side, and choose the faucet farthest from where the water line enters the house, so water pulls through the whole run.

The drip does two jobs. Moving water is harder to freeze, and the open tap bleeds off the pressure that would otherwise burst the pipe.

2. Open the cabinet doors. Under sinks on exterior walls, open the vanity and cabinet doors so household heat can reach the pipes.

3. Keep the heat steady. Do not lower the thermostat at night. Hold the same temperature day and night through the cold snap.

A higher heating bill for a few nights is nothing next to the cost of a burst pipe and the cleanup that follows.

4. Close the garage door. If water lines run through the garage, keep the door shut to hold out the cold.

The lasting fixes: insulation, sealing, and hose bibs

Dripping faucets is a night-of patch. The real protection is done before winter, when it is dry and warm.

Start where pipes freeze first. The worst spots are unheated attics, crawl spaces, garages, and pipes run against uninsulated exterior walls.

One analysis of 433 burst pipe claims found unheated attics to be the most common failure point, so prioritize the coldest, most exposed runs.

Insulate the pipes. Foam pipe sleeves cost only a few dollars at any hardware store and slide right on. Wrap every pipe in an unheated space.

Seal the drafts. Caulk and foam the gaps where cold air sneaks in around pipes, dryer vents, and wiring on exterior walls.

Remember, a draft on a pipe is more dangerous than still cold air, so closing those air leaks matters as much as the insulation itself.

Handle the outdoor faucets. In fall, disconnect and drain every garden hose. A hose left on a spigot traps water that freezes back into the wall.

If you have an interior shutoff for an outdoor hose bib, close it and open the outside tap to drain the line. Add an insulated faucet cover for a few dollars more.

The 55 degree rule and leaving your home in winter

Empty houses freeze. Most winter pipe disasters happen while no one is home to notice the cold creeping in.

The rule is simple. When you leave in cold weather, never set the thermostat below 55 degrees, no matter how long you will be gone.

This matters for your insurance too. Carriers often deny a frozen-pipe claim if the home was left unheated, so cutting the heat to save money can cost you the payout.

If a claim ever comes back denied over a heat or maintenance question, know that a denied water damage claim can be fought with the right evidence.

For a weekend away, 55 degrees plus a dripping faucet is usually enough. Leave the cabinet doors open too.

For a long absence or a vacant property, go further and winterize the plumbing so there is no water left to freeze.

That means shutting off the main water valve, then opening every faucet and flushing the toilets to drain the system down.

Drain from the lowest tap in the house and let gravity pull the water out. Pour a little plumbing antifreeze into drains and toilet bowls to protect the traps.

What to do if a pipe is already frozen

The first sign is usually a faucet that gives only a trickle, or nothing at all, on a cold morning. That pipe is frozen but may not have burst yet.

Move fast, because a frozen pipe is a pipe under building pressure. Thawing it gently relieves that pressure before it splits.

Open the faucet that the frozen pipe feeds. As the ice melts, running water speeds the thaw and gives the pressure an escape.

Apply gentle heat to the frozen section. A hair dryer, an electric heating pad, a space heater kept clear of anything flammable, or towels soaked in hot water all work.

Start at the faucet and work back toward the cold spot, so meltwater can drain out rather than get trapped behind fresh ice.

Never use an open flame. A blowtorch, propane or kerosene heater, or charcoal stove is a leading cause of house fires during freezes.

Keep the main valve open while thawing so pressure can push loosened ice out. But know where that main shutoff is, because you may need it in seconds.

If you cannot reach the frozen pipe, or it will not thaw, call a plumber before it bursts rather than after.

What to do if a pipe has already burst

If a pipe splits, this is now a flooding emergency, and seconds matter.

Shut off the main water valve immediately to stop the flow. Then open faucets to drain the remaining pressure from the lines.

Photograph everything before you clean up. Insurance pays on documented loss, so capture the burst, the water line, and every damaged item first.

Then get the water out and the drying started fast. If it reached a lower level, our guide on what to do first when a basement floods walks the emergency in order.

Wet drywall and framing hold water long after the surface looks dry, which is why drying out the walls is its own careful job that decides whether mold follows.

When the water is back on after any thaw or repair, turn it on slowly and walk the joints, valves, and ceilings, watching for the crack that ice was hiding.

When to call a plumber or restoration pro

A drip and a hair dryer handle most freezes. Some situations are past the DIY line.

Call a plumber if a pipe will not thaw, is behind a finished wall you cannot reach, or has already burst and needs a repair.

Call a restoration company if the burst soaked drywall, flooring, or insulation, because that water hides in the cavities and grows mold if it is not dried right.

It helps to know what water damage restoration costs before you call, so the estimate is not a second shock on top of the first.

None of that is failure. Prevention is cheap, but once a pipe bursts, the right pro dried out fast is what keeps a small repair from becoming a big one.

Keep reading

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