Frozen Pipes: How to Prevent Them and What to Do When One Bursts

A burst pipe while you're at work is one of those home disasters that runs fully before you can intervene. The water keeps flowing until you shut it off, and by the time you're home the damage is established in the drywall, flooring, and insulation around the pipe. The prevention requires about ninety minutes of fall prep. The recovery from a burst can take weeks and cost thousands. This is an area where the preparation math is not complicated.

Which pipes freeze first

Pipes freeze when exposed to cold air long enough for the water inside to reach 32 degrees Fahrenheit. The pipes most at risk are the ones with the least insulation between them and the outside: outdoor faucet supply lines, pipes in unheated garages or crawl spaces, pipes in exterior walls without adequate insulation, and supply lines in cabinets on exterior walls.

The outdoor faucet situation is the most preventable and most commonly missed. The standard hose bib on an exterior wall has a supply pipe that runs back through the wall to the interior shut-off. If a garden hose is left connected to that faucet, it traps water in the faucet body even after you turn off the interior valve. That trapped water freezes. The fix: disconnect garden hoses every fall before the first freeze, then turn off the interior shut-off valve and open the outdoor faucet briefly to drain the supply stub.

Prevention: insulation and heat

pipe insulation foam sleeves are a standard first defense. They don't generate heat — they slow the transfer of cold to the pipe. In a crawl space that drops to twenty degrees, insulation alone may not be sufficient for an extended cold event. In a garage that drops to thirty-five degrees on cold nights, insulation is usually adequate.

For pipes in genuinely cold unheated spaces — exposed pipes in an unheated garage, water lines running through an uninsulated exterior wall section, outdoor pipes in a northern climate — heat cable (also called pipe heating cable or heat tape) is the right tool. It's an electrical resistance wire that wraps around the pipe and turns on automatically via thermostat when temperatures approach freezing. Install it per the manufacturer's instructions on the pipe before insulating over it.

The simple behavioral preventions: let cold-side faucets drip during extreme cold events (moving water is harder to freeze than standing water), open cabinet doors under bathroom and kitchen sinks on exterior walls to allow house heat to reach the pipes, and keep the house temperature above 55 degrees Fahrenheit even if you're traveling — the savings from dropping below that are not worth the risk.

Finding and thawing a frozen pipe

Signs of a frozen pipe: faucet produces no water or very reduced flow, possibly a frosty or bulging section of pipe visible in a crawl space or basement. If you find it before it bursts, the goal is gradual warming.

Open the faucet the frozen pipe supplies — this gives the water somewhere to go when it melts and helps confirm when flow returns. Apply heat to the frozen section starting from the faucet side and working toward the colder area: a hair dryer is the safest tool, or electric heating pads, or warm wet towels. Never use an open flame. Never apply concentrated heat to one spot — you want gradual even warming along the run.

If you can't locate the frozen section or can't access it, this is a plumber call.

When a pipe has already burst

The first action is the main water shut-off. Know where yours is before this happens. It's typically in the basement near where the water service enters the house, or in a utility area. Turning it off stops the flow while you assess the damage. Open faucets throughout the house to drain any remaining pressure in the lines.

Document everything with photos before any cleanup begins — this matters for insurance claims. Call your insurance company the same day, not after cleanup. Call a plumber for the pipe repair; this is not the time to DIY if you haven't done plumbing repairs before.

What I'd skip

Skip the habit of turning the heat completely off when traveling in winter. A house at fifty-five degrees is warm enough to protect pipes in most situations; a house at forty degrees or below in a cold climate is a frozen pipe waiting for the right cold snap.

The bottom line: pipe insulation, heat cable on the vulnerable runs, and the outdoor faucet shutdown routine are all the prevention most houses need. An afternoon of this work in October is the alternative to a very expensive spring repair.