How to Keep Pipes From Freezing Without Power

By NorthBriar Editorial Team · Published Aug 12, 2026 · Reviewed per our editorial policy

The furnace stopped when the lines went down, the house is cooling, and the question is no longer whether to act but in what order. Good news first: you have more time than panic suggests, and the two most effective moves need no electricity at all. Here's how to keep pipes from freezing without power, in the order the hours demand.

How long do you have?

The moment you lose power in a cold snap, start the clock on your pipes freezing, but know how long that clock actually runs.

Unprotected pipes in unheated spaces typically freeze within 6-8 hours once temperatures sit at or below 20°F, per Angi's 2025 review of freeze data, and that figure describes pipes already exposed to the cold, like a crawl space run or an attic line. The pipes inside your heated envelope have a bigger cushion: a closed-up house loses its warmth over many hours, not minutes, and Building Research Council field tests found unheated interior spaces hold a few degrees above the outdoors even in sustained cold. The colder the night and the leakier the house, the shorter your runway. But in most homes, in most outages, you have hours before freezing becomes likely, not minutes.

Use them in this order.

First: safety, because outage heating kills people

• Generators run outside only, never in a garage, basement, or near a window. Carbon monoxide from improvised indoor power and heat is the deadliest part of any winter outage.
• No open flames, charcoal, camp stoves, or unvented propane heaters indoors, and never point any flame at a pipe; the American Red Cross prohibits open-flame devices around plumbing entirely.
• Don't heat the house with a gas oven. It isn't vented for it.
• If gas is in the air at any moment, get everyone out first; dial 911 and the gas utility once you're outside.

Hour one: slow the heat loss

Keeping pipes from freezing during a power outage is a heat-retention game first. Think of the house as a cooler you're trying to keep warm: you can't add heat, so keep what you have where the plumbing is.

• Close every exterior door, and keep trips outside short.
• Shut doors to rooms with no plumbing; let the rooms with pipes borrow the remaining warmth.
• Open cabinet doors under every sink so room air reaches the supply lines, straight from the Red Cross playbook.
• If it's daytime, open curtains on the sunny side; close all of them after dark.
• Stuff a towel against the biggest door drafts. Small move, real effect on the coldest runs near exterior walls.

Then: get the water moving

Even when the power is out, municipal water keeps flowing, and a trickle of moving water resists freezing far better than standing water. That's the logic behind the Red Cross advice: keep a cold drip going at every faucet an exposed line feeds. In an outage, run a cold-water drip at the faucets farthest from where the main enters the house and at any fixture on an exterior wall: a steady drip, not a stream, holding freezing off at the most vulnerable pipes. Where a vulnerable sink has separate hot and cold handles, open each one a hair. The full technique, including which faucets matter most, is in how to drip faucets.

One caveat from that table deserves repeating: if your pipes rely on heat cable through winter, an outage removes that protection exactly when you need it. And if you're on a well, your pump is down. The water still in the lines is all you have, so skip the drip and move straight to the next step sooner.

If the outage will outlast your heat: drain the system

When the forecast says days, not hours, or the house is dropping toward freezing and you're leaving, stop defending the water and remove it:

1. Shut off the main water valve where the line enters the house.
2. Working from the top floor down, open all faucets on both sides, hot and cold, and don't close them.
3. Flush the toilets until the tanks stop refilling.
4. Open the low-point drain valve if the house has one.

An emptied system has nothing to freeze; this is the same principle as a full vacant-house winterization, minus the trap antifreeze you'd add for a longer vacancy. If the outage stretches on, that page covers the complete version, including the water heater. Note that the heater should have its breaker switched off during the outage anyway, so a repowered electric unit never fires on a drained tank.

When the power comes back

Restore heat, then check before you celebrate. Close the dripped faucets, walk the house, and check the runs where freezing was likeliest for the signs a pipe froze during the outage: a fixture with no flow or a weak trickle, frost on an exposed pipe, damp drywall or ceilings. If a pipe did freeze, it's most dangerous right now: as it thaws, any split it caused starts leaking. Our guide on what to do about frozen pipes covers finding and thawing the blockage; if you see water escaping anywhere, shut the main back off, keep clear of wet areas near outlets, and call (800) 555-0173. NorthBriar will match you with a licensed local plumber any hour of freeze season.

Before the next outage

Every one of tonight's improvisations has a permanent version: insulation on the pipes that flirted with freezing, rerouting for the line that always freezes first, a shutoff valve you can actually find in the dark. The winterization hub walks through them in order of payoff, worth an hour once the lights are back on, so the next time the power goes out, the pipes are not the emergency.