Preventing Frozen Pipes

Seattle area homes are more vulnerable to frozen pipes than homes in genuinely cold places, because they were built for a climate that rarely freezes hard. Water lines run through vented crawlspaces and uninsulated exterior walls, and when an arctic front drops us into the teens, those lines freeze while a Spokane house shrugs it off. Prevention is simple and cheap: insulate exposed pipes, manage the crawlspace vents, drip the vulnerable faucets during a hard freeze, and know how to thaw a frozen line without starting a fire. This is the full playbook.

Why do Seattle homes freeze before colder cities do?

Building practice follows climate. In cold climates, code and habit put water lines inside heated space. Around Puget Sound, where an average January night sits in the mid 30s, generations of builders ran supply lines through vented crawlspaces, garages, and exterior walls with little or no insulation. That works fine 360 nights a year.

Then comes the exception. During the December 2022 arctic outbreak, the region spent days in the teens, and our technicians spent the following weeks repairing split pipes in crawlspaces from Tacoma to Mount Vernon. The physics is unforgiving: water expands about nine percent when it freezes, and a full, blocked pipe has nowhere to send that pressure except through its own wall. Copper splits, PEX fittings let go, and older galvanized pipe cracks. The flood usually arrives at thaw, when the ice plug melts and the split opens up, often while nobody is watching.

Which pipes in your home are at risk?

Cold needs access. The pipes that freeze are the ones the outside air can reach.

• Crawlspace lines, especially runs near foundation vents where freezing air blows straight across them.
• Pipes in exterior walls, most often kitchen and bathroom supplies on a north-facing wall. Cabinets block room heat from reaching them.
• Hose bibs with hoses still attached, which trap water in the faucet body and the wall behind it.
• Garage lines, common in homes where the laundry or a utility sink lives in an unheated garage.
• Attic and bonus room runs above the insulation layer, a classic split-level surprise.

An hour with a flashlight tells you which of these your house has. Foam pipe insulation costs little and slides on bare runs in minutes. It will not protect a pipe through days of deep cold on its own, but it buys hours, and hours are usually what the difference comes down to.

What is the hard freeze playbook?

When the forecast shows nights below about 25 degrees, especially several in a row, run this list the evening before.

1. Drip the vulnerable faucets. Open the cold tap to a pencil-thin stream at the fixture farthest from the water main and at any faucet on an exterior wall or with a freeze history. Moving water resists freezing, and more importantly the open tap relieves pressure so that even if ice forms, the pipe is far less likely to burst. The water cost for a few nights is trivial next to a repair.
2. Open the cabinet doors. Under-sink pipes on exterior walls freeze inside closed cabinets that block the room's heat. Open them and let warm air in.
3. Close or cover the crawlspace vents. Foam blocks or reusable covers keep the coldest air off the pipes. Open them again after the freeze, because a Puget Sound crawlspace needs airflow the rest of the wet season.
4. Use heat tape where insulation is not enough. For chronic problem runs, UL-listed heat cable with a built-in thermostat works well. Follow the listing exactly: no overlapping the cable on itself, no wrapping insulation over a cable not rated for it, and plug it into a GFCI outlet. Damaged or bargain-bin heat tape causes fires, which is why CPSC guidance treats it as equipment to inspect every season.
5. Hold the heat steady. Keep the house at its normal temperature day and night. This is not the week for aggressive setbacks.
6. Find your main shutoff and test it. If a pipe does burst, closing that valve within a minute or two is what separates a repair from a renovation.

Leaving town? Keep the heat at 55 or above, leave the drip running, and ask someone to check daily. The worst damage we see is in empty houses where a burst line ran unnoticed.

What should you do if a pipe freezes?

No water at one fixture while the rest of the house works usually means an ice plug in that branch. Act early, because a frozen pipe that has not burst yet can often be saved.

1. Keep the affected faucet open. It relieves pressure and gives meltwater a path out.
2. Find the frozen section if you can. Follow the line toward the cold: crawlspace, exterior wall, garage. Frost on the pipe or a bulge marks the spot.
3. Warm it gently. A hair dryer, a heat gun on low kept moving, warm towels, or a space heater placed safely in the room all work. Start at the faucet end and work toward the blockage.
4. Never use an open flame. A propane torch on a frozen pipe starts house fires every winter, and it can also boil trapped water into steam and burst the pipe you were saving. Slow and warm beats fast and hot.
5. Watch what happens at thaw. If water reappears and pressure holds, you got lucky. Insulate that run so it does not repeat.

If the pipe has already split, you will know at thaw: water where it should not be, a hiss inside a wall, or a ceiling stain spreading. Shut off the main, open faucets to drain the system, kill power to any wet area, and call for help. Our pipe repair team handles burst lines, and our emergency dispatch line gets a plumber moving. Real people answer early and late, 6 AM to 6 PM every day. A frozen section that keeps recurring in an older galvanized system is also a sign the house may be a candidate for repiping rather than repair after repair.

How does this fit into overall winter prep?

Freeze protection is one chapter of a shorter book. Hose bibs, heat pump settings, ventilation, and the rest of the seasonal checklist live in our companion guide to winterizing a Puget Sound home. Do the standing items in October, and keep this article's playbook for the week the arctic air actually arrives. The two together cover the whole season.

Common questions

At what temperature do pipes freeze in Seattle homes?

Exposed lines in crawlspaces and exterior walls start becoming a risk when air temperatures hold below about 25 degrees for six or more hours. Insulated pipes and pipes in heated space tolerate far more. The danger scales with duration: one cold night is rarely the problem, while the third night of a cold snap is.

Should I drip hot, cold, or both?

Cold is the priority, since supply lines freeze first, but on a fixture served by both, a slight drip on each side protects both lines. On single-handle faucets, set the handle to the middle so both supplies flow.

Does dripping faucets waste too much water?

A pencil-thin stream for a few nights uses a small number of gallons per faucet per day. One burst pipe can release hundreds of gallons an hour into your framing. Run the drip during hard freezes and do not feel bad about it.

My pipes froze but never burst. Do I still need to do anything?

Yes. Freezing stresses pipe walls and joints even without a visible failure, and a run that froze once will freeze again in the same spot. Insulate that section, fix the airflow that chilled it, and if it is old galvanized pipe, have it inspected, since corrosion plus freeze stress is how the next event becomes a burst.

What to do next

Walk your crawlspace and exterior walls this fall, wrap what is bare, and tape the playbook inside a kitchen cabinet before the first arctic front. If you find a pipe already weeping, a bib that will not shut off, or a freeze-prone run you want protected properly, the Eco plumbing team can help. Visit our pipe repair page, book online, or call (206) 970-1031, 6 AM to 6 PM every day.