Why Are My Pipes Frozen? Understanding Winter's Biggest Plumbing Threat

It’s a frigid winter morning. You turn on the kitchen faucet to make coffee, and nothing comes out but a sputter of air. Instant panic sets in.

If the temperature outside has dropped significantly below freezing (typically 20°F or lower), and you have no running water, it is almost certain that you have a frozen pipe somewhere in your home's plumbing system.

This is not just an inconvenience; it is an impending disaster. When water freezes, it expands by about 9%. That expansion creates tremendous pressure inside the pipe—up to 3,000 psi—which is easily enough to split copper, PVC, or steel pipes wide open.

Before you grab a blowtorch (spoiler: do not grab a blowtorch), you need to understand why this happened and the safe steps to take next.

At TruePlumber, we help homeowners in cold climates, from Idaho to the Northeast, battle freezing plumbing every winter. Here are the main reasons your pipes froze and what to do about it.

The Science: Why Do Pipes Burst?

Contrary to popular belief, ice doesn't usually burst the pipe right where the blockage is. The burst actually happens because of pressure buildup between the ice blockage and the closed faucet.

The ice acts like a plug. As more water tries to flow toward the faucet and freezes, the remaining liquid water is compressed further and further until the pipe can no longer contain the pressure. This is why opening faucets immediately is crucial (more on that below).

The 3 Most Common Culprits

Why did your pipes freeze when your neighbor's didn't? It almost always comes down to location and insulation.

1. Poorly Insulated Exterior Walls

Pipes that run inside exterior walls—the walls that touch the outside air—are the most vulnerable. If the insulation inside that wall is thin, settled, or missing, the cold will penetrate right through the drywall and freeze the pipe hidden behind it. This is common under kitchen sinks that face an outside window.

2. Unheated Crawlspaces, Attics, and Garages

Any plumbing that runs through an unconditioned (unheated) space is at high risk.

Crawlspaces: Drafty crawlspaces are the number one location for frozen pipes.
Attics: Pipes running over the ceiling insulation are essentially outside.
Garages: Water lines running through garage walls or ceilings often freeze if the garage door is left open or is poorly insulated.

3. Sneaky Air Drafts

Even a tiny crack in your foundation or a gap where a cable line enters your house can allow a jet of freezing cold air to blow directly onto a pipe. It doesn't take much cold air, if aimed precisely at a copper pipe, to freeze it solid over several hours.

Immediate Steps: Triage and Thawing

If you suspect a frozen pipe, you need to act immediately to relieve pressure and try to thaw it safely.

Step 1: Open the Faucets Turn on the affected faucets (both hot and cold) all the way. Even if no water comes out, opening the valve relieves the pressure building up behind the ice dam, which is what actually causes the pipe to burst.

Step 2: Locate the Freeze Follow the pipes from the faucet backwards into colder areas (basements, crawlspaces, cabinets on exterior walls). Look for pipes that are frosted over or bulging.

Step 3: Thaw Gently (NO OPEN FLAMES) If you can access the frozen section, try to thaw it gently.

USE: A hair dryer, a portable space heater kept at a safe distance, or towels soaked in hot water wrapped around the pipe. Start heating from the faucet side and work your way back toward the frozen area.
NEVER USE: A blowtorch, kerosene heater, charcoal stove, or any open flame. You risk starting a house fire or overheating the water inside the pipe, causing it to explode as steam.

When to Call a Professional

Sometimes, DIY efforts aren't enough. You need professional frozen pipe thawing and repair services if:

You can't find the freeze: The blockage might be inside a finished wall or underground.
You see a crack: If the pipe has already split, shut off your main water supply immediately. As soon as that ice thaws, water will gush out. You need emergency burst pipe repair.

Prevention is Cheaper Than Repair

Once you get the water flowing again, you must ensure it doesn't happen next time the temperature drops. The only permanent solution is professional pipe insulation and freeze protection. This involves properly wrapping vulnerable pipes and, in extreme cases, installing electric heat tape to actively warm the pipes during deep freezes.

Don't wait for the next polar vortex. Connect with a TruePlumber professional today to winterize your home.