Direct answer: A frozen pipe in an exterior wall usually shows up as little or no water at one fixture during a cold snap, while nearby fixtures still work. Start by checking whether the pipe is frozen but intact or already split, because a hidden burst inside the wall changes the job fast.
Most likely: The most likely cause is a supply pipe running through a poorly insulated outside wall, often behind a sink cabinet, vanity, or shower wall where cold air is getting in.
Start with the fixture that lost flow, then check the wall and cabinet around it for cold spots, frost, bulging paint, or dampness. Reality check: sometimes the pipe thaws and the real problem starts afterward when a split opens up under pressure. Common wrong move: blasting one hot spot with a torch or space heater and cooking the wall, insulation, or pipe.
Don’t start with: Do not start with an open flame, high-heat gun, or by cutting the wall open before you know whether the pipe is frozen, leaking, or both.
A sink, toilet, shower, or hose-bib branch on an outside wall has stopped or nearly stopped, but other fixtures still have normal pressure.
Start here: Check whether both hot and cold are affected or just one side. That tells you whether one branch is frozen or the whole fixture area is getting hit by cold air.
One handle has normal flow and the other barely dribbles or does nothing.
Start here: Trace that specific supply line back through the vanity, sink base, or basement ceiling below the wall. A single frozen branch is more likely than a fixture failure during a cold snap.
The back of the sink cabinet, vanity wall, or access panel is much colder than the room, sometimes with frost or condensation.
Start here: Look for open gaps around pipes, missing insulation, or a cabinet packed tight enough that room heat cannot reach the plumbing.
Flow returns after temperatures rise, but now there is dripping in the wall, wet drywall, or a musty smell.
Start here: Assume the pipe may have split while frozen. Shut off water to that branch or the house before the wall gets wetter.
This is the classic setup when one fixture on an outside wall loses flow during hard cold while the rest of the house still works.
Quick check: Feel the wall cavity area from the room side and inside the cabinet. If that zone is much colder than nearby interior walls, the pipe route is exposed to outside cold.
A small gap around a pipe, sill plate, hose-bib, or exterior penetration can create a direct cold draft right onto the pipe.
Quick check: Use your hand to feel for moving cold air around the back of the cabinet, under the sink, or where pipes pass through the wall or floor.
Pipes behind closed sink cabinets freeze more often because warm room air never reaches the back wall.
Quick check: Open the cabinet doors and compare the temperature near the back panel to the room. If it is sharply colder, trapped cold is part of the problem.
If the line thawed and now you have wet drywall, staining, or dripping, the freeze event likely turned into a burst-pipe repair.
Quick check: Look for fresh water marks, bubbling paint, damp base trim, or the sound of water moving in the wall when no fixture is running.
You can safely warm a frozen pipe that is still intact. A split pipe inside the wall needs water control first.
Next move: If you find no signs of leakage, you can move on to careful thawing and monitoring. If you find wet materials, active dripping, or water sounds in the wall, stop treating this like a simple freeze and control the water first.
What to conclude: A dry wall cavity points toward a frozen but intact supply line. Wet finishes or fresh staining strongly suggest the pipe has split or a fitting has opened up.
You want the freeze point before you add heat. Exterior-wall freezes are usually local, not random.
Next move: If you can narrow the freeze to one wall section or one branch, you can warm that area gradually and watch it closely. If several fixtures on different walls are affected, this page may be too narrow and the freeze may be in a larger branch line.
What to conclude: A single dead hot or cold side usually means one frozen supply branch. Multiple dead fixtures point to a broader freeze farther upstream.
Slow, even warming is the safest way to thaw a frozen pipe in a wall without damaging the pipe or the wall around it.
Next move: If water starts flowing again and the area stays dry, keep warming gently for a while longer so the line fully clears. If there is still no flow after steady gentle warming, the freeze may be deeper in the wall or the pipe may already be damaged.
A lot of freeze damage does not show up until pressure is fully back on the line.
Next move: If the wall stays dry and pressure is normal, you likely caught the freeze before the pipe split. If moisture appears, pressure drops again, or you hear water in the wall, shut off that branch or the house main and plan for a wall-open repair.
If you do not deal with the cold path, the same pipe will freeze again on the next hard snap.
A good result: If the area stays dry and protected from cold, you have moved from emergency response to prevention.
If not: If the pipe is inaccessible, repeatedly freezing, or already split inside a finished wall, this is the point to bring in a plumber.
What to conclude: A one-time freeze can often be stabilized. Repeat freezes usually mean the pipe location or wall insulation needs a more permanent correction.
Repair Riot may earn a commission from qualifying purchases, at no extra cost to you.
If flow drops during a hard freeze and the wall area stays dry, the pipe may just be frozen. If you see wet drywall, bubbling paint, dripping, staining, or hear water moving in the wall after thawing starts, assume it has split and shut the water off.
Only if the pipe area is accessible and you can use gentle moving heat from a safe dry location. Do not overheat one spot, and do not use any heat source you cannot keep under constant watch. Warm room air into an open cabinet is usually the safer first move.
Yes. Open the affected side of the faucet so melting ice can relieve pressure and you can tell when flow starts to return.
That usually means one local supply branch froze in an exterior wall, often behind a kitchen or bathroom cabinet. It is much more common than a whole-house freeze when the other fixtures still have normal pressure.
Sometimes, but not always. Insulation helps on accessible pipe, but repeated freezes usually mean cold air is leaking into the wall or the pipe route is too exposed. Air sealing and better wall protection matter just as much.
That usually means the pipe is still in a very cold wall and is refreezing, or the thaw was only partial. Keep the area warm, check for hidden leaks, and make a permanent fix to the cold exposure before the next freeze.