Kim Reeves
You walk into the kitchen at 7 a.m., turn on the faucet, and nothing comes out. Not a trickle. Just that particular silence that means you’re about to have a bad morning. I’ve been on job sites where this happened in houses that were supposedly “winterized,” and I’ve talked homeowners down from panicking at 9 p.m. on a Sunday when no plumber was answering. The good news: frozen pipes under a sink are one of the more manageable cold-weather problems you can handle yourself. The bad news: a lot of people make the situation dramatically worse in the first five minutes.
Let’s fix that.
First, Figure Out What You’re Actually Dealing With
Before you touch anything, open the cabinet doors under the sink and look. You’re checking for two things: whether the pipes are visibly frozen (frost on the outside of copper or PVC is a clear sign, as is slight bulging) and whether anything has already cracked or split. A frozen pipe that hasn’t burst yet is a Tuesday-morning problem. One that’s already failed is a different situation entirely.
Under-sink pipes freeze for a reason. Usually it’s an exterior wall situation, a cabinet that doesn’t get any heat, or a kitchen or bathroom that sits above an uninsulated crawl space. Knowing which applies to you matters because you’ll want to address the root cause after you deal with the immediate crisis, or this will happen again next January.
If you see a crack, a split seam, or water already pooling, stop. Close the main water shutoff to the house before you do anything else. Then call a plumber, because thawing a pipe that’s already failed just turns a frozen problem into a flooding problem. The water doesn’t care that it’s inconvenient.
If the pipe looks intact, you’re good to proceed.
How to Actually Thaw It
| Method | Time Required | Best For | Safety Level |
|---|---|---|---|
| Hair dryer | 10-20 minutes | Most under-sink situations | Very safe |
| Heating pad | 20-30 minutes | Longer frozen sections, tight spaces | Safest |
| Heat lamp/space heater | 30-45 minutes | Unknown frozen location, hands-off approach | Safe |
| Warm water pour | 10-15 minutes | Exposed copper or galvanized pipes | Safe |
The goal is slow, even heat applied to the section of pipe that’s frozen. The mistake I see most often is people going straight for a propane torch. Don’t. Under a sink, you’ve almost certainly got wood cabinetry, particle board shelving, cleaning supplies, and other flammable stuff within inches of the pipe. Open flame in that space is genuinely dangerous, and it also heats the pipe too fast and unevenly, which can crack it even without a pre-existing split.
Here’s what actually works, in order of what I’d reach for first:
A hair dryer on its highest setting is the right tool for most of these situations. Point it at the frozen section and work from the faucet end toward the wall, which lets water escape as it melts rather than trapping steam pressure in the middle. Keep it moving. Don’t hold it six inches from one spot for two minutes straight. You’re warming the pipe, not soldering it.
A heating pad wrapped around the pipe works especially well for longer frozen sections or copper pipes in tight spaces where you can’t maneuver a hair dryer comfortably. Wrap it around, set it to medium, and wait. This takes longer, maybe 20 to 30 minutes, but it’s the safest method by a fair margin. I’ve used this in finished spaces where I absolutely could not risk any heat damage to nearby surfaces.
Heat lamp or space heater positioned to warm the general area works too, particularly if you can’t identify the exact frozen spot. Open the cabinet doors, point a ceramic space heater at the interior from a couple feet away, and give it 30 to 45 minutes. This is slower but hands-off, which has its own appeal at 6 a.m.
One thing that genuinely surprises people: warm (not hot) water poured over the pipe, caught with towels underneath, can work reasonably well on exposed copper or galvanized pipes. It’s low-tech and it works. Just have something down to soak up the water, because it’ll go everywhere.
Throughout all of this, keep the faucet open. Even a small drip means water is moving, which means the thaw is working. The pressure release also reduces the risk of the pipe splitting if there’s any weak spot you didn’t notice.
What Not to Do (And Why This List Exists)
I’ll be direct about this because I’ve seen the aftermath in person.
No propane or butane torches under a sink. Ever. Not even “just for a second.” The number of house fires that start in kitchen cabinets during pipe thawing is not small. It’s also possible to superheat water inside a closed pipe section to the point where it basically explodes. This is not a theoretical risk.
Don’t pour boiling water on plastic pipes (CPVC or PVC). You can warp or crack them instantly, and then you have a much more expensive repair.
Don’t crank the heat and walk away for hours. If the pipe does fail while you’re not watching, you want to be there to shut the water off immediately. Stay close until the water is running again.
Don’t ignore the problem and hope it self-resolves. Pipes that freeze tend to freeze harder as temperatures drop overnight, and the longer a frozen section sits, the more stress accumulates at weak points.
Once the Water’s Running Again
The first thing you do when water starts flowing is check every connection point you can see under that sink. Look at the joints, the shutoff valves, the P-trap, anywhere water could weep. Sometimes a pipe will develop a hairline crack during freezing and you won’t see it until water pressure returns. Give it five full minutes of water flow and a careful look.
Then address the actual problem: why was that pipe cold enough to freeze?
Open cabinet doors under sinks on exterior walls during cold snaps. This sounds almost too simple, but it genuinely works because it lets the heated air from the room reach the pipes. If you’ve got a bathroom vanity on an exterior wall that’s frozen twice now, it’s worth having someone add some insulation behind the cabinet back panel. That’s a two-hour job and about $30 in foam insulation.
Pipe insulation sleeves (the foam tube kind you find at any hardware store, about $4 for six feet of 1/2-inch) are worth putting on any pipe run that’s remotely close to an exterior wall or unheated space. Put them on in October, not January.
Plug-in pipe heating cables are a legitimate solution for chronic problem spots. They’re thermostat-controlled, they turn on automatically when temps drop below about 38°F, and they draw very little power. Something like the Frost King Electric Pipe Heating Cable runs around $25 to $40 for an 6-foot section and has a solid track record. For under-sink pipes that freeze every single winter, it’s the right answer.
A Contrarian Take Worth Hearing
Sources
Most freeze-prevention advice focuses on insulation, and insulation is good, but I’d argue that the more important variable is air movement. A pipe surrounded by still, cold air in a sealed cabinet will freeze faster than a pipe with the same amount of insulation but a crack of warm air getting to it. This is why opening cabinet doors works so well and why closing up every gap in your cabinet’s exterior wall backing can sometimes make things worse, not better.
The traditional advice to “seal drafts” under kitchen sinks to keep cold air out is correct when the cold air is coming from outside (around pipe penetrations through the exterior wall, for example). But sometimes homeowners go further and fully seal the cabinet interior from the room, which cuts off the warm indoor air that was keeping the pipe from freezing. The goal is to block outside cold air while allowing indoor warm air to circulate. It’s a subtle distinction but it matters.
Photo: Magda Ehlers via Pexels
