Frozen Pipes: How to Thaw Them Safely (and What Not to Do)

Frozen Pipes: How to Thaw Them Safely (and What Not to Do)

A frozen pipe is one of those problems that can feel manageable right up until it suddenly isn’t. The pipe itself may not have burst yet — but the real danger often comes during the thaw, when water pressure builds up behind a blockage of ice. Handle it carefully and you can get things flowing again without incident. Rush it or use the wrong method and you risk a flood.

Here is what to do, what to avoid, and when to put the phone down and call us instead.

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Step One: Confirm You Have a Frozen Pipe

The most common signs are:

• No water from a tap when the supply is otherwise on
• Visible frost or a slight bulge on an exposed pipe (particularly in a loft, garage, or outside wall)
• A strange smell from a tap or drain — ice can trap gases as well as water

If you can hear running water behind a wall but nothing is coming out of the tap, turn off your stopcock immediately. That sound may mean a pipe has already split.

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How to Locate the Frozen Section

Start at the tap that has stopped working and trace the pipe back towards the cold. Pipes most likely to freeze are those that run through:

• Uninsulated loft spaces
• External or cavity walls
• Garages and outbuildings
• Under kitchen or bathroom units on outside walls

Once you have a rough idea of where the blockage is, you can begin thawing — slowly and carefully.

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Safe Ways to Thaw a Frozen Pipe

Warm air from a hairdryer

This is the most practical method for accessible pipes. Set the dryer to a low or medium heat and work from the tap end of the pipe back towards the frozen section. This allows the meltwater to escape as you go rather than building up pressure behind the blockage.

Keep the dryer moving. Do not hold it in one spot.

Warm (not hot) water in a cloth

Soak a cloth or towel in warm water, wring it out, and wrap it around the frozen section. Repeat as it cools. This is slower but very controlled — useful for pipes near electrical fittings where a hairdryer would be risky.

A hot water bottle

Placed directly over the pipe, a hot water bottle is a gentle and safe option. It works well on copper pipes in tight spaces where a hairdryer cannot reach easily.

Gentle ambient heat

If the frozen pipe is in a loft or cupboard, simply opening the hatch and letting warm air in from the house can be enough, given time. Leave it an hour before trying the tap again.

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What Not to Do

These approaches cause more problems than they solve:

• Never use a naked flame. A blowtorch, lighter, or candle can cause a pipe to expand and split instantly, and can set fire to nearby joists, insulation, or lagging. This is one of the most common causes of house fires in winter.
• Do not pour boiling water directly onto a pipe. The sudden temperature change can crack copper or split plastic fittings.
• Do not crank the heating up and walk away. Rapid thawing without monitoring means you will not notice a burst until water is already coming through the ceiling.
• Do not ignore a bulge or crack in the pipe. If the pipe looks deformed, turn off the stopcock and call a plumber before attempting any thawing.

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The Burst Risk on Thaw

It is worth understanding why pipes burst when they thaw rather than when they freeze. Ice actually creates a plug in the pipe. As the ice melts, water pressure rebuilds behind that plug. If the pipe wall has already been weakened by the expansion of ice, that returning pressure is enough to split it open.

This is why slow, controlled thawing from the tap end matters — it gives the water somewhere to go as pressure builds, rather than forcing it through a weak point in the pipe wall.

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Preventing It Next Time

• Lag any pipes in unheated spaces — loft lagging kits are inexpensive and straightforward to fit
• Leave heating on a low setting (around 13–15 °C) when the property is empty in cold weather
• Know where your stopcock is before you need it — usually under the kitchen sink or near the front door

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When to Call Us

If you cannot locate the frozen section, if the pipe is inside a wall, if you can see visible damage, or if water has already started to appear anywhere — stop and call us straight away. Attempting to thaw a split pipe will only make the situation worse.

We cover the TW postcode area around the clock, every day of the year.

Call Emergency Plumbers TW: 07725 479493

We will assess the situation quickly, isolate the problem, and carry out any repairs needed — so you are not left dealing with a flood on top of a freeze.