Boiler Not Working After a Frost? Here’s Why and How to Fix It

There’s something lovely about the first frosty morning of the year. Crisp air, sparkly lawns and the frozen windscreen everyone pretends they’re not dreading. Then you turn on the shower and find your boiler has stopped working overnight.

Every year, the first hard frost brings a wave of calls from people whose heating has suddenly stopped. The good news? In most cases the boiler isn’t broken at all. Frost is the culprit, and it’s often a quick fix.

Here’s our engineers’ guide to why frost stops boilers working, how to get your heating back on and how to frost-proof your home before the next cold snap.

Why frost stops your boiler working

Most modern boilers are condensing boilers. They’re very efficient, but they produce a small amount of water as they run. That water drains away through a plastic pipe called the condensate pipe, which often runs outside to a drain.

When there’s a frost, the water sitting in that pipe can freeze and block it. The water then has nowhere to go, so the boiler shuts itself down to stay safe. It isn’t broken. It’s just frozen.

Has frost got to your boiler? How to tell

Most people don’t realise frost can affect their boiler, so it’s easy to assume something serious has gone wrong. Frost is the likely cause when:

• There was a frost last night. This is the biggest clue. If the cars and lawns are white, your condensate pipe may be frozen too.
• It worked fine yesterday. No warning signs or strange noises beforehand. It just won’t start this morning.
• It’s showing a fault code or flashing light. Many boilers show a fault code that looks like an ignition problem, which can make it seem more serious than it is.
• You can hear gurgling. Water that can’t drain away can make a bubbling or gurgling sound from the boiler.
• Your neighbours are having the same trouble. If others nearby are without heating on the same frosty morning, it’s a good sign the frost is to blame.

To check, look for a white or grey plastic pipe coming out of the wall near your boiler and running down to a drain outside. If it’s frosted over, has ice at the end or at a bend, or feels frozen solid, you’ve found the problem.

How to thaw a frozen condensate pipe safely

If you’re comfortable doing it, you can often get your heating back on yourself:

1. Find the frozen part. It’s normally the section outside, especially near the end or at a bend where water collects.
2. Warm it gently. Pour warm water (not boiling) along the pipe, or hold a hot water bottle or warm wheat bag against it. Boiling water can crack the pipe.
3. Reset your boiler. Once the ice has cleared, follow the reset steps in your boiler’s manual. It may take a minute or two to fire back up.

Please don’t climb ladders or reach for pipes high up the wall, especially on icy ground. If you’re not sure, or your boiler still isn’t working after thawing the pipe, give us a call and one of our engineers will help.

How to frost-proof your home this winter

Insulate exposed pipes. Pipe lagging is cheap, easy to fit and one of the best ways to stop frost getting to your pipes. Start with your condensate pipe if it runs outdoors, then any pipes in the loft, garage or along outside walls.

Keep your heating ticking over on frosty nights. When a frost is forecast, leave your heating on a low setting rather than switching it off completely. Many boilers and thermostats also have a frost protection setting that kicks in automatically when temperatures drop.

Don’t switch off when you’re away. If you’re going away over winter, keep the heating on low so the house never gets cold enough for pipes to freeze.

Fix dripping taps. A slow drip can freeze in the pipe overnight and cause a blockage.

Know where your stop tap is. It’s usually under the kitchen sink. If frost ever bursts a pipe, turning it off quickly can save a lot of damage. Check it turns easily now, before the cold sets in.

Get your boiler serviced before the frosts. Your boiler works hardest in winter, so a service now means it’s ready for the coldest mornings. If yours hasn’t had one in the last year, it’s a great time to book.

What to do if frost bursts a pipe

Frost doesn’t only affect your boiler. Water expands when it freezes, so pipes in colder parts of your home can split, and you often only find out when they thaw. If that happens:

1. Turn off the water at the stop tap straight away.
2. If water is near any electrics, switch off the electricity at the consumer unit and don’t touch anything wet.
3. Open your cold taps to drain the system.
4. Catch what water you can with towels and buckets.
5. Call us and we’ll get it sorted.

Peace of mind whatever the weather

If you’d rather not worry about frosty mornings at all this winter, our Care Plans start from £12.50 a month. They include your annual service and cover repairs up to £500, so if the frost does catch you out, you know who to call and you won’t be hit with a surprise bill.

We’ve been keeping homes warm through frosty winters since 1980. Whether your boiler has stopped, needs a service or you just want some advice, our friendly team is here to help.

Call us on 0330 383 0000 or book online.