How to tell if pipes are frozen & what to do if they burst

When the weather turns cold, if your central heating isn’t working and there’s no water from one or more taps, you may have frozen pipes. As inconvenient as that may be, there’s also a danger that your pipes may burst, which will be much more than an inconvenience.

Let’s talk about why pipes freeze, how you can tell if they are frozen and what to do if they freeze or burst.

Why do water pipes freeze, and what makes them burst?

If the temperature in your house drops below zero, any water in your pipes is likely to freeze. This is more likely to happen if you’ve been away from home for a length of time and left the heating turned off to save on energy costs, but it can even happen while you’re at home if there are sections of pipe that are particularly exposed to cold, such as in the roof space or on outside walls of the house.

As water expands when it freezes, the pressure inside the pipe increases. With no place to escape, the water will eventually rupture the pipe at its weaker points.

How can I tell I have a frozen pipe?

If the entire system is frozen, the earliest signs might be that your boiler isn’t working, because if water isn’t being fed to the boiler it will cut off as a safety measure. Toilet cisterns that don’t refill after flushing and taps that don’t run water are other tell-tale signs.

Before assuming the worst, check with your neighbours to see if they have a similar problem. If they do, contact the water company: the problem probably lies with the public water supply, not your pipes.

Frozen pipes can also be confined to one part of the system, particularly if a section of pipework is exposed to cold: outside taps and pipework that is run across lofts or along outside walls are more vulnerable. Just one tap or toilet system not working while the heating and the rest of the water supply are fine might be a sign of this.

Knowing you have a frozen pipe is a start, but finding where it is frozen can be harder, particularly as freezing at one section of the pipework can cause bursting at another. Tips on how to locate it are included in the next section, but if you have any doubts, call in a professional plumber.

What should I do if I have a frozen pipe?

If you suspect or find you have a frozen pipe, quick action can often prevent it from bursting. Here’s what to do, in 5 steps:

1: Shut down the system

The first thing you want to do is to reduce the amount of water that could potentially flood your house if the pipe bursts.

Look for a stopcock on the rising main (the pipe bringing all water into the house) and turn this off. The stopcock is often located under the sink in the kitchen.

If you have a cold water tank (usually found in the loft), turn off the supply from the tank.

With no water supply, it’s also important that you turn off your boiler and if you have one, your immersion heater.

2: Locate the frozen section of the pipe

You’ll need to start by assuming the frozen section could be anywhere, and that more than one section might be frozen. Checking taps and toilet flushes for running water. Any that don’t might be a clue to the whereabouts of the blockage, but remember you’ve already isolated the water supply so there will only be so much water left in the system.

Visible pipes are more likely to freeze as they aren’t protected by lagging. Look for sections of pipe that are particularly cold to the touch, have patches of frost on them or are bulging slightly.

Inspect these sections of pipe, looking for water seeping out or damp patches on surfaces surrounding the pipe. Remember that as the water is frozen, this might be preventing water from escaping until it thaws, so it might still be relatively dry. Examine the pipe for cracks.

If you do find signs of damage to the pipe, don’t continue with steps 3 and 4. Scroll down to the section “What should I do if a water pipe bursts?” in this article and follow those instructions.

Step 3: Get ready to thaw the pipe

As the pipes begin to thaw, you will need to safely release the built-up pressure caused by the frozen water. This can be done by opening the taps nearest to the frozen sections and letting the water escape. If these taps empty into a sink, first make sure the sink outlet pipe isn’t also frozen so the water can drain off.  

Clear the area around the frozen section. This will prevent movable items from water damage and give you space to move and work. Shield any electrical wiring and sockets, and have plenty of towels and containers to hand, just in case the pipe does burst.

Step 4: Thaw the pipe

Frozen pipes should always be thawed cautiously: aggressive heat sources such as a blowtorch, heat gun or lighter should definitely not be used.

A hairdryer on its lowest heat setting can be used to thaw a frozen pipe, but use this with caution as if the pipe does burst and escaping water sprays onto the hairdryer it could cause an electrical shock.

Safer methods include placing a hot water bottle, a microwaveable heat pad or a towel soaked in hot water on the pipe.

Start by thawing the end of the frozen pipe section that is nearest to the open tap and work your way back as the water melts.

Step 5. Restoring the system

Once all frozen pipe sections have been thawed, close all open taps and gently turn the water back on. Check the system again thoroughly for leaks as, with the system back under normal pressure, small leaks that might have gone undetected while you were defrosting the pipes might now be visible.

If it all seems fine, we recommend you read our article “Protect Your Pipes This Winter” for ideas on how you can prevent or reduce the risk of frozen pipes in the future.

What should I do if a water pipe bursts?

If a pipe bursts, prompt action must be taken to reduce the severity of water damage to the structure and contents of your house. Discovering a burst pipe while it is still frozen improves your chances of repairing it before any damage occurs. If the burst pipe is leaking water be very careful, particularly if the leak is near electrical appliances, equipment, outlets or wiring.

The first two steps are urgent and must be done immediately

Step 1: Isolate and drain the water system

If you haven’t done this already, stopping the water supply and emptying the system will reduce the risk of flooding.

Turn off your mains water supply via the stopcock on the rising main as it enters the house (often located under the kitchen sink) and the water supply from the cold water tank (if you have one, this may be in the loft).

Turn off your boiler, and your immersion heater (if you have one).

Open all taps and flush all toilets to remove all residual water from the system.

Step 2: Disconnect the electrical supply

If your electricity mains junction box is at a safe distance from the burst pipe, turn off the main switch to isolate the whole electrical system in the house. This will protect against electrical hazards caused by water connecting with wiring, sockets and electrical equipment.

Don’t take risks here: if you can’t easily access the junction box, call for an electrician.

Step 3: Contact a professional plumber

Unless you have successfully tackled plumbing jobs before and have confidence in your skills, this isn’t the time to start experimenting with DIY plumbing. If there’s been a severe drop in temperatures you’re probably not the only one with frozen and burst pipes, so good plumbers might be hard to get hold of. Use the WaterSafe online directory to ensure you get a fully qualified plumber in your area.

If your plumber can’t come immediately but you want to temporarily repair the pipe, you may be able to seal it with heavy-duty duct tape from a local DIY shop, hardware store or even a supermarket. This won’t repair it enough for you to be able to use the water until the plumber arrives, but at least it will prevent further leakages.

Step 4: Record the damage and clean up

In situations like this, our first instinct is to clean up the mess, but bear in mind that if you are claiming damages from your insurance company they will need evidence of the damage. Take pictures before and during the clean-up process as these will support your claim and keep damaged items for inspection, even if they are so badly damaged they cannot be salvaged.

If the burst pipe was upstairs, check your ceilings on the floors below as water will quickly damage plaster or plasterboard ceilings. Immediate signs of damage will be bulges as the water saturates the ceiling. Place a bucket under the bulge to catch the water and use something sharp to poke a hole in the bulge. Although the damaged part of the ceiling will need to be replaced, this will release the water and prevent it from travelling further across the ceiling and causing wider damage.

Before starting to clean up, contact your insurance company for advice on making a claim and the steps you need to take to have the damage fixed. Keep all receipts for work done on the repairs and for the replacement of any damaged items, as the insurance company will need these.

Once you have spoken to the insurance company the cleaning up can begin. Start by removing anything from the affected area that might yet be affected by the water: as the humidity will be considerably higher than usual for a while yet, this should include anything that might spoil if damp for a long time including furniture, electrical items, photographs and books.

Anything that may have absorbed a lot of water such as ceilings, carpets and soft furnishings in the immediate area of the leak, should be removed from the property. When your electrician considers it safe to reconnect your electricity, use a dehumidifier to draw water back out of the fabric of the building.

Once your plumber has repaired the burst pipes, check that all taps that you opened earlier have been switched off and then reopen the taps from your mains water supply and the cold water tank. Your plumber may help you to do this and check that everything is working properly.