How to Prevent Pipes from Freezing (Winter Prep Checklist)
Prevent frozen pipes with foam insulation, heat tape for problem runs, and an overnight drip when temps hit 20°F. Crawl space to exterior wall, under $50.
Quick answer: Prevent frozen pipes by insulating exposed runs in crawl spaces, garages, and under exterior-wall sinks with foam pipe sleeves, sealing gaps where cold air enters the building envelope, and keeping interior temps above 55°F even when the house is empty. On nights forecast to drop below 20°F, let cold-side faucets on exterior walls drip overnight. Those four steps cover roughly 90% of residential pipe freeze events. Materials run $25-50 for most homes.
Pipes freeze in predictable places. Not random sections of a house, but the runs that pass through the three coldest spots: unheated crawl spaces, uninsulated garages (especially near an overhead door), and kitchen or bathroom cabinets on exterior walls. Add the outdoor spigots, and that is basically the full risk list.
Most freeze-and-burst events happen in February, when a cold snap hits a house that was not quite prepared in November. The fix is straightforward: foam insulation on vulnerable pipe runs, caulk on the gaps where cold air leaks in, and knowing which temperature threshold to pay attention to. This guide walks through all of it.
What You’ll Need
Tools:
- Utility knife (for cutting foam insulation to length)
- Staple gun or foil duct tape (to secure loose seams)
- Caulk gun
Supplies:
- Foam pipe insulation sleeves (sized to match pipe diameter, usually 1/2 inch or 3/4 inch ID; about $2-4 per 6-foot section at any hardware store)
- Self-regulating heat tape for long cold runs (Frost King or Easy Heat models rated for pipe contact; around $15-30 for a 6-foot section)
- Foam backer rod or fiberglass insulation (for stuffing gaps around pipe penetrations)
- Caulk or small can of spray foam
Step 1: Find Your Vulnerable Pipes
Walk through the predictable cold spots before insulating anything. Five minutes of reconnaissance saves you from insulating pipes that do not need it and missing the ones that do.
Crawl space: Bring a flashlight and look for bare pipe runs near the exterior rim joist, anywhere near an uninsulated crawl space vent, or where supply lines enter through the foundation wall. Cold air settles into crawl spaces and moves fast through open vents.
Garage: If supply lines run through the garage wall or along the garage ceiling, they are at risk. An unheated garage tracks outdoor temperature closely overnight. Any pipe in that space is exposed.
Under kitchen and bathroom sinks on exterior walls: The cabinet creates a pocket of air that stays colder than the room. Cabinet doors that stay closed overnight trap that cold air against the back of the cabinet where the pipes come through the wall.
Attic spaces: Less common, but homes with supply lines running through an unheated attic to upstairs bathrooms have had freeze problems in hard winters. Check if any runs go through attic space above unconditioned areas.
Mark or photograph anything that looks like bare copper, bare CPVC, or bare PEX tubing in any of these spots. That is your insulation list.
Step 2: Insulate Exposed Pipe Runs
Foam pipe insulation sleeves split lengthwise and snap over the pipe without any tools beyond a knife to cut lengths. Each section handles one pipe diameter, so match what is printed on the pipe or measure the outer diameter. Standard residential supply lines are 1/2 inch or 3/4 inch nominal.
Push cut ends of adjacent sections together so there are no gaps. Tape the seams with foil duct tape, especially in crawl spaces where the insulation can get disturbed by foot traffic or animals.
For longer runs in consistently cold spaces, consider adding self-regulating heat tape on top of the foam. Frost King’s self-regulating models heat only when they sense low temperatures and are rated for direct pipe contact, which matters because not all heat tape is safe against PEX or CPVC. Wrap the tape in a spiral around the pipe, add the foam sleeve over it, and plug it into an outlet before the first freeze. Unplug it in spring.
Cut the foam insulation a few inches past any metal fitting or transition piece. Fittings sit at the cold end of an insulated run and are often the first spot to freeze.
Step 3: Seal Cold-Air Entry Points
Insulation slows heat transfer, but gaps and holes are where cold air gets in directly. A half-inch gap around a pipe where it passes through a rim joist or exterior wall framing can let in enough cold air to overwhelm even well-insulated pipe.
Use foam backer rod stuffed into larger gaps, then caulk over it. For pipe penetrations through exterior walls, a small can of spray foam (the minimal-expansion type, not the big gap-and-crack kind) fills the annular space around the pipe neatly. Let it cure, then trim it flush.
While you are at it, check the door between the house and an attached garage. Cold air drifting from the garage into a utility space or mechanical room is a common path for freeze damage. A properly fitted door sweep on that interior door stops a meaningful amount of cold air transfer.
Step 4: Keep Interior Temps Consistent
The American Red Cross recommends keeping home temperatures above 55°F even when the house is unoccupied, and most heating professionals prefer 60°F as a safer floor for homes with supply lines near exterior walls. The extra few degrees of thermostat setpoint costs a few dollars a day, well below what a burst pipe event costs.
Turning the heat to 50°F to save money while away for a week in January means gambling that overnight lows while you are gone do not reach the pipes in the garage or crawl space. For most of the northern US, that is not a reliable bet.
If a property will be vacant for the whole winter, the more dependable option is to drain the system entirely rather than maintain heat. See Step 6 for the drain procedure.
The furnace itself should be in working order before you rely on it to protect pipes through a hard winter. If it has not had a maintenance pass in the last year, the furnace pre-winter checklist covers what to look for before the first cold snap.
Step 5: Let Faucets Drip on Extreme Cold Nights
When overnight temperatures are forecast below 20°F, let the cold-side faucet on exterior-wall fixtures drip slowly through the night. Moving water does not freeze as readily as a static column.
Two things to get right:
Run the cold side only. That is the line running through the exterior wall. Hot water supply lines typically run through interior wall space and are less exposed.
If you have a single-handle faucet, set it toward cold. On two-handle faucets, open only the cold handle.
Kitchen faucets on exterior walls matter more than bathroom faucets on interior walls. Focus on the fixtures attached to the runs you identified in Step 1.
Opening cabinet doors under exterior-wall sinks on those cold nights helps. Warm room air circulates to the back of the cabinet where the supply lines enter through the wall.
Step 6: Know How to Shut Off the Water Fast
If a pipe does freeze, the priority is catching it before it bursts. A frozen but intact pipe can sometimes be thawed by working a hair dryer on low heat along the pipe from the faucet end back toward the frozen section. Never use an open flame.
If a pipe has already burst or you hear running water behind a wall, shut off the main water supply immediately. Do not spend time trying to find the exact break location. Get the water off first.
The process for locating and operating the main shutoff is covered in how to shut off water to your house. Knowing where it is before you need it in an emergency is worth five minutes now.
For houses that will sit vacant all winter, shut off the main supply and open every faucet to drain the system, starting with the lowest fixtures and working up. After the lines drain, pour a small amount of plumber’s antifreeze into each p-trap so the traps do not dry out and let sewer gas in. The water heater should also be drained if the house will be unheated.
Common Mistakes
Skipping outdoor faucets. Frost-free sillcocks manage light freezes on their own, but only if no garden hose is attached. A connected hose traps water in the pipe regardless of sillcock type. Disconnect hoses before the first hard freeze and address outdoor faucet shutoffs now. The full procedure for winterizing outdoor faucets takes about ten minutes per faucet.
Using roof de-icing cable on supply pipes. Standard roof and gutter heating cable is not rated for pipe contact, particularly plastic pipe. Self-regulating models labeled specifically for water pipe use (Frost King, Easy Heat pipe cables) are the right product.
Stopping the foam insulation short of the fittings. The transition fitting or valve at the end of an insulated run is often the coldest point because it sits just past the edge of where the insulation ends. Run the foam sleeve a few inches past any fitting.
Turning the heat off entirely in a vacant house. Even in a drained system, residual water in p-traps and the water heater can cause problems. If the pipes are drained, the water heater should be drained as well, or the heat should stay above 40°F.
When to Call a Pro
If the same section of pipe has frozen and burst more than once, the pipe routing itself is the problem. Foam insulation is a workaround; the permanent fix is rerouting that section through interior wall space. A plumber can assess whether that is feasible.
If you suspect a pipe has frozen inside a wall and is still intact, a plumber with a pipe-thawing unit can clear it faster and more safely than working through drywall. Some contractors have low-pressure steam equipment that heats the pipe from the outside.
Pipes embedded in a concrete slab foundation are a professional job. The access requirements and risk of damaging the slab make DIY freeze recovery impractical.
FAQ
At what temperature do pipes freeze? Pipes exposed to outdoor air or in unheated spaces typically begin to freeze when temperatures hold below 20°F (-7°C) for several hours. Pipes inside insulated walls can withstand colder temperatures than that, but extended cold snaps below 20°F can reach them through rim joist areas and foundation penetrations. Wind chill accelerates freezing for pipes in crawl spaces with open vents.
Should I drip faucets all winter or only on the coldest nights? Only when the forecast drops below 20°F. Continuous dripping wastes water and provides no meaningful additional protection compared to the targeted overnight drip approach. If you are away for an extended stretch and cannot monitor the forecast, a slow drip on each exterior-wall fixture is a reasonable precaution for the whole trip.
What type of pipe insulation works best? Closed-cell foam pipe sleeves are the standard for most residential runs: they do not absorb moisture, stay dimensionally stable over time, and are fast to install. For pipes in a crawl space or garage that stays near freezing for weeks at a time, self-regulating heat tape plus foam gives better protection than foam alone. In climates that regularly see sustained temperatures below 0°F, the heat tape is the primary layer and foam is secondary.
Can I use fiberglass batt insulation instead of foam sleeves? Fiberglass can be wrapped around pipes as a temporary measure, but it absorbs moisture over time and compresses, which reduces its effectiveness. Foam sleeves hold their shape and do not absorb water. Use fiberglass only as a short-term fix while waiting for foam to arrive.
Do PEX pipes need the same treatment as copper? PEX tolerates freezing better than copper or CPVC because it expands slightly before bursting, but it is not immune. Repeated freeze cycles fatigue the connection fittings, which are the weakest points in a PEX system. Insulate PEX in exposed locations the same way you would copper.
How do I tell if a pipe is already frozen? No water flow at one or more fixtures while other parts of the house have normal flow is the first signal. A pipe in a crawl space or along a wall will feel noticeably colder to the touch than adjacent sections. Do not try to force faucets open if there is no flow; the pressure behind an ice plug is already high, and opening more fixtures does not help.
Will pipe foam work on plastic supply lines? Yes. Foam sleeves sized to the pipe’s outer diameter work on PVC, CPVC, and PEX the same way they work on copper. CPVC is more brittle at very low temperatures than PEX, so exterior-wall CPVC runs in cold climates benefit from heat tape in addition to foam, rather than foam alone.