Frozen Pipe: How to Thaw It Safely and What to Do Next

Before You Thaw: Turn Off the Water

The first thing to do when you suspect a frozen pipe is to turn off the water at the main stopcock — not to start thawing. Here's why: a frozen pipe may already have a crack. Ice expands as it freezes, and the pressure inside a blocked pipe can be enough to split copper or plastic. You won't know the pipe has cracked until the ice melts and water starts escaping. If the water is still on when that happens, you have a burst pipe flooding your property.

Turn off the stopcock first. Then thaw. Then restore the water supply cautiously, checking for leaks as pressure returns.

How to Locate the Frozen Section

Frozen pipes don't always announce their location obviously. Signs include: a tap that produces no water or only a trickle despite the stopcock being open, a toilet that won't refill, or a section of pipe in an exposed area (loft, garage, external wall) that feels hard and cold compared to surrounding sections.

Pipes most at risk are those in unheated spaces: loft runs near the cold water tank, pipes along external walls with inadequate insulation, pipes in garages or outbuildings, and any outdoor tap supply pipe. Start your investigation in these locations.

Safe Thawing Methods

Hairdryer

The most practical domestic tool for thawing a frozen pipe. Work from the tap end (the outlet) back towards the frozen section — this allows water to escape as the ice melts rather than building up pressure behind the thawing section. Keep the dryer moving; don't hold it stationary on one point. Works well on copper and plastic pipes in accessible locations.

Warm Towels or Hot Water Bottle

For pipes in awkward locations where a hairdryer can't reach safely, wrapping the frozen section in towels soaked in warm (not boiling) water or applying a hot water bottle is effective if slower. Replace the towels or bottle as they cool. Patience matters here — thawing slowly is safer than applying direct heat.

Warm Air in the Space

For a frozen loft pipe or a frozen section in an enclosed space, placing a fan heater or portable radiator in the space and letting the ambient temperature rise is a gentle, effective approach. Takes longer but avoids direct heat application to the pipe.

What Not to Do

• Never use a naked flame — a blowtorch, candle, or gas lighter directly on a pipe is a fire risk and will cause localised overheating that can fail solder joints or cause plastic pipes to deform
• Never pour boiling water directly onto a pipe — the thermal shock can crack a pipe that's already under ice-expansion stress
• Don't force water through with a pump — if a section is fully frozen, additional pressure behind it risks splitting the pipe

How to Tell If the Pipe Has Already Burst

As the pipe thaws, watch for: water beginning to drip or flow from a joint or section of pipe that didn't previously drip, a bulge or visible deformation in the pipe wall, or water beginning to appear on walls, ceilings, or floors near the frozen section. If any of these appear as the pipe thaws with the stopcock closed, you have a cracked or burst pipe that needs immediate repair before the water is restored.

At this point, call an emergency plumber — do not restore the water supply until the damaged section is repaired. Read our guide to water coming through your ceiling if the damage has affected the floor above.

After Thawing: Preventing a Repeat

Once the pipe is thawed and confirmed intact, the work isn't finished. The conditions that caused it to freeze will cause it to freeze again in the next cold snap. Our guide to preparing your plumbing for winter covers insulation, frost protection settings, and the other steps that make frozen pipes unlikely to recur. Our guide on preventing frozen pipes has more detail on lagging and frost protection measures.

If the frozen pipe is in a loft, garage, or other unheated space and isn't easily insulated, our plumbing repairs team can re-route the pipe through a more protected route or install appropriate lagging. Book online or call 02039514510.

Frequently Asked Questions

How long does it take to thaw a frozen pipe?

With a hairdryer applied carefully, a short frozen section of 30–60 cm typically thaws within 20–40 minutes. Longer frozen runs or pipes in very cold locations (deep loft, exposed outside wall) can take considerably longer. Do not rush — slow and steady thawing is safer than aggressive heat.

Can a frozen pipe burst even after thawing?

Yes — a pipe can have a hairline crack from ice expansion that is held closed while ice is present, then opens and leaks once the pipe is fully thawed. This is why turning off the stopcock before thawing and carefully restoring the supply in stages is important. Watch the pipe and surrounding area carefully for 30 minutes after restoring water to confirm there are no leaks.

Is a frozen pipe covered by home insurance?

Damage caused by a burst frozen pipe — water damage to floors, ceilings, contents — is typically covered under the escape of water section of a standard home buildings and contents policy. The cost of repairing the pipe itself is usually not covered (it's considered a maintenance item). Document the damage before clearing up, and report to your insurer promptly.

Can I prevent outdoor taps from freezing?

Yes — turn off the outdoor tap supply using its indoor isolation valve and drain the tap by opening it after isolation. For added protection, fit an insulating cover over the outdoor tap body itself. If your outdoor tap doesn't have an indoor isolation valve, fitting one is a straightforward job that makes winterisation much easier. Ask us to add one on a routine call-out.