What Temperature Do Pipes Start to Freeze Inside Walls?
Last updated October 26, 2026
The short answer
Why 20 Degrees Matters
The freezing point of water is 32 degrees Fahrenheit, but pipes inside walls usually need colder air to actually freeze. The wall cavity traps some heat from your home, so the pipe stays warmer than the outside air until temperatures fall well below freezing. When the outdoor temperature stays around 20 degrees or lower for several hours, the pipe can reach freezing.
Your home's insulation plays a big role. A well-insulated wall might protect pipes until temperatures drop even lower, while a poorly insulated wall with drafts can let pipes freeze at 25 degrees. The pipe material matters too, as copper conducts cold faster than plastic. Knowing your home's weak spots helps you act before trouble starts.
Signs Your Pipes Are Freezing
Watch for reduced water flow from faucets, which often means ice is forming inside the pipe. You might hear a gurgling sound or notice frost on exposed pipe sections. If you see any of these signs, open the faucet slightly to keep water moving and help relieve pressure.
Another clue is a sudden drop in water pressure or no water at all from one fixture. Act quickly if you suspect freezing, because the ice can expand and crack the pipe. Shut off your main water valve if a pipe bursts, then call a plumber for the repair and the pros for any water cleanup.
How to Prevent Frozen Pipes
Keep your thermostat at a consistent temperature, even at night, so heat reaches the wall cavities. Open cabinet doors under sinks to let warm air circulate around pipes. Insulate pipes in unheated areas like garages, crawl spaces, and exterior walls using foam sleeves or heat tape.
Seal gaps and cracks in your home's exterior to stop cold drafts from reaching pipes. Disconnect garden hoses and shut off outdoor spigots before winter. If you leave for several days, set the heat to at least 55 degrees and ask someone to check your home periodically.
Bullets
Keep cabinet doors open under sinks on cold nights
Let faucets drip slowly during extreme cold spells
Insulate pipes in unheated spaces with foam sleeves
Seal wall cracks and gaps with caulk or spray foam
Know where your main water shutoff valve is located
Drain and shut off outdoor spigots before winter
What to Do If a Pipe Bursts
If a pipe bursts, shut off the main water valve right away to stop the flooding. Then turn off electricity in the affected area if water is near outlets or appliances. Document the damage with photos for your insurance claim, and start removing standing water to prevent further damage.
Call a plumber to repair the broken pipe, and contact local water damage pros for the cleanup. They can dry out walls, floors, and belongings to prevent mold growth. Water damage in walls can spread quickly, so addressing it within a day or two makes a big difference.
Shut off the main water valve immediately
Turn off electricity in flooded areas for safety
Remove standing water with buckets or a wet vacuum
Move furniture and rugs out of wet areas
Use fans and dehumidifiers to help dry surfaces
Take photos of the damage for your insurance records
When to Call the Pros
You can handle small drips and minor moisture yourself, but significant water damage needs professional help. If water has soaked into drywall, insulation, or flooring, the pros have the equipment to dry it properly. Without thorough drying, mold can start growing within a couple of days.
The pros can also inspect behind walls to find hidden moisture and assess structural damage. They use moisture meters and industrial fans to dry areas you cannot reach. If you live in Bellingham, keep your shutoff valve location written down so you can act fast in an emergency. Policies vary, and your insurer decides what is covered.
Water spread to multiple rooms or floors
Drywall is soaked or sagging
You smell a musty odor after drying
The water came from a sewage or flood source
You cannot dry the area within 48 hours
Need help right now?
Water keeps spreading into floors and walls, so it is worth acting early. Calls are answered 24/7.
Call Now (360) 685-7801Frequently asked questions
Can pipes freeze if the heat is on?
Yes, pipes can still freeze if the heat is on but not reaching the wall cavity. Poor insulation, drafts, or unheated rooms can keep pipes cold enough to freeze. Keep your thermostat above 55 degrees and open cabinet doors to help warm air circulate.
How long does it take for pipes to freeze?
It depends on the temperature, insulation, and pipe location. At 20 degrees, pipes can freeze in about 6 to 12 hours. At 0 degrees, freezing can happen in less than 2 hours. The longer the cold lasts, the higher the risk.
What temperature should I keep my house to prevent frozen pipes?
Set your thermostat to at least 55 degrees, even when you are away. This helps keep wall cavities warm enough to prevent freezing. If you leave for several days, keep the heat on and ask someone to check your home regularly.
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