Frozen Pipes: Where They Freeze First and How to Check Before Winter

Pipes freeze first where water lines sit in cold air that house heat doesn't reach. That means unheated crawl spaces and attics, garages, sink cabinets on outside walls, and any spot where wind leaks in around a pipe. Research from the Building Research Council at the University of Illinois found that uninsulated pipes in an unheated attic started to freeze once it got down to about 20°F outside. A pipe sitting in a draft can freeze even when it's warmer than that.

The fix is an hour with a flashlight this fall. Find every pipe that sits in a cold spot, insulate or seal what you can reach, and learn where your main shutoff is before you need it.

01Why the Leak Shows Up Somewhere Else

Pipes usually don't split right where the ice is. Once an ice plug blocks the pipe, more water keeps freezing and expanding. That pushes the trapped water toward a closed faucet, and pressure builds in that stretch until the weakest point gives. So the split can be several feet from the frozen spot, and you often won't see it until the ice melts and water starts running.

This is also why the standard advice is to open the faucet while you thaw. It gives the trapped water and pressure a way out.

02This Is Not Only a Northern Problem

State Farm reported more than 20,000 frozen-pipe and winter water claims from 2024 through June 2025. It paid out over $628 million, and the average claim topped $30,000. The top five states by total cost were Illinois, Oregon, Washington, Texas and Tennessee.

Three of those five are places where a hard freeze doesn't come every week. When a cold snap hits a house built for mild winters, pipes in attics and outside walls have no protection. Wherever you live, if your area ever drops into the teens, do this walk-through.

03The Walk-Through: Where to Look

Pick a cold morning if you can. A cold pipe or a draft is easy to feel with your hand and easy to miss on a warm afternoon.

1. Sink cabinets on outside walls

Kitchen sinks under a window are the classic trouble spot. Bathroom vanities on an outside wall are a close second.

• Open the cabinet and put your hand flat on the back wall. If it's noticeably colder than the room, the pipes behind it are too.
• Look where the supply lines come through the wall or floor. Gaps around the pipe let cold air pour straight onto the plumbing. Seal small gaps with caulk and bigger ones with low-expansion spray foam.
• Shine a light into the back corners for old water stains. They mean this spot has leaked before.

2. Pipes inside exterior walls

You can't see these, but you can work out where they are. Look for any fixture on an outside wall: a laundry hookup, a second-floor bathroom, a wet bar. Then ask what's on the other side of the wall. A bathroom sitting over an unheated garage, or a room that hangs out past the foundation, puts pipes in a cold cavity.

You won't open walls for this. Just make a list of these fixtures, because they're the ones to drip on the coldest nights. If you're already hunting drafts, the same outlet-cover and light check from finding drafty windows and doors will show you which walls are leaking cold air.

3. Crawl spaces

This is where a lot of freezes start. Go in with a good light and look for:

• Bare supply pipes running along the joists or near the foundation vents
• Fiberglass batts that have fallen down and left pipes uncovered
• Foundation vents left open into winter, or missing vent covers
• Gaps at the rim joist where daylight or wind gets in, especially around the spot where the main water line comes in

Our crawl space check covers the moisture and pest side of the same trip.

4. Garages

Garages often have water lines for a laundry room, a utility sink, a water softener or a water heater. Follow every pipe you can see and note any that run along an outside wall or ceiling. Keep the big door shut on cold days. A door left open all afternoon turns a garage into an outdoor space.

5. Attics

In much of the South and West, plumbing runs through the attic, sometimes right above the insulation. If you have pipes up there, check that they're buried under the insulation (on the heated side), not lying on top of it. Our attic insulation and ventilation guide shows you how to get around safely.

6. Basements and the main line

In an unfinished basement, check where the main water line comes through the foundation. That wall is cold, and the rim joist above it is often poorly sealed.

7. Outside

Hose bibs and sprinkler lines are their own job. Disconnect the hoses and drain what you can. The full steps are in winterizing outdoor faucets.

04Protecting What You Found

Foam pipe insulation is the cheapest fix there is. A 6-foot sleeve for 1/2-inch pipe costs about $2 to $4 at home centers (as of October 2026). Measure the outside diameter of your pipe before you buy, since sleeves are sized to fit. Tape the seams and butt the joints tight. A 2-inch gap at an elbow is where the ice will form.

Seal the air leaks. Insulation slows heat loss, but it won't stop a pipe from freezing in a steady wind. Close the gaps at rim joists, sill plates and pipe holes first, then insulate.

Heat cable makes sense for a run you can't keep warm any other way, like a supply line in a crawl space that hits the single digits. Use a thermostatically controlled cable made for water pipes, install it exactly as the instructions say, and plug it into a GFCI-protected outlet. Our GFCI testing guide shows how to check one.

Find and test your main shutoff. It's usually where the water line comes in, close to the meter in a basement, crawl space or garage, or in a curb box out by the street. Turn it off and back on now so you know it works. Tag it so everyone in the house can find it. If it's seized or drips, have a plumber replace it while nothing is flooding.

05The Cold-Night Routine

When a hard freeze is forecast:

• Let cold water drip from faucets fed by pipes in outside walls or other cold spots. A slow, steady drip is enough.
• Open the sink cabinet doors so room air reaches the pipes. Move the cleaning supplies if you have kids or pets.
• Keep the thermostat at the same setting day and night. Skip the overnight setback during a cold snap.
• If you'll be away, leave the heat on and set no lower than 55°F.
• Keep the garage door closed.

06Signs a Pipe Is Frozen

• You turn on a faucet in freezing weather and get a trickle or nothing at all.
• One faucet works and another, usually the one on an outside wall, doesn't.
• A toilet doesn't refill after a flush.
• Frost is visible on an exposed pipe in a crawl space or basement.

If the whole house goes dry at once, the freeze is probably on the main line where it enters, or the problem is outside on the utility side. Call your water utility as well as a plumber.

07What to Do When One Freezes

1. Open the faucet the pipe feeds, both hot and cold. Running water helps melt the ice, and the open faucet lets pressure out.
2. Find the frozen section if you can reach it. Look for the coldest stretch, often where the pipe passes an outside wall, a vent or a gap.
3. Apply gentle heat. Use a hair dryer, an electric heating pad, a space heater kept well away from anything that can burn, or towels soaked in hot water. Start at the faucet end and work back toward the frozen spot.
4. Never use an open flame. No torches, propane heaters or kerosene heaters. They can damage the pipe and start a fire inside the wall.
5. Keep heating until full pressure comes back, then check the other faucets in the house. If one pipe froze, others may have too.
6. Watch for leaks as it thaws. Look under the sink, along the crawl space joists and on the ceiling below. Our guide to finding a hidden water leak helps if you're not sure.

If water starts spraying or dripping, shut off the main valve right away. Then call a plumber and your insurance company.

08When to Call a Plumber

• You can't find the frozen section, or it's inside a finished wall or ceiling.
• You've applied heat for a while and the water still won't flow.
• A pipe has split, bulged or started leaking.
• The main line or the water meter area is frozen.
• The same pipe freezes every winter. That's a routing or insulation problem that needs fixing, not something to thaw again every year.

09Before the First Hard Freeze

• Feel the back of every sink cabinet on an outside wall
• Walk the crawl space, garage and attic, and list every exposed pipe
• Seal gaps where pipes and the main line come through walls and rim joists
• Sleeve exposed pipes with foam insulation, with no gaps at the joints
• Disconnect hoses and winterize outdoor faucets
• Find, test and tag the main water shutoff
• Write down which faucets to drip on the coldest nights

This fits in nicely with the rest of the fall home inspection checklist.

Sources (6)

• State Farm: Frozen pipe claims data, 2024 through June 2025
• State Farm: Preventing frozen pipes and steps if they freeze
• Consumer Reports: How to keep pipes from freezing
• Lakeway MUD: Building Research Council 20°F threshold and why pressure bursts pipes
• American Red Cross frozen pipe tips (PDF)
• Lowe's: 1/2-in x 6-ft foam pipe insulation (price reference)

Photo by GWizUK on Pixabay.