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Frozen Condensate Pipe

How To defrost your condensate pipe - Help Guide 

Follow this easy step-by-step breakdown of the process - see below


If you’ve had a new gas boiler installed in the last 15 years, it will most likely be a high-efficiency condensing boiler.  The good news is that a high efficiency gas boiler is good for your home and your pocket. In simple terms, a condensing boiler can extract heat from the water vapour in exhaust gasses by passing the gasses through something called a condenser. The condensed water vapour (now just water) then leaves the boiler through something called a condensate pipe.

The condensate pipe is usually a white PVC-U pipe, similar to one you may find on a washing machine or sink waste pipe which usually goes outside into a drain. It’s worth noting that boiler condensate can be slightly corrosive to certain materials, especially metals. That’s why condensate pipes are usually made of plastic and not metal.

Is it important?

Yes! Once the water vapour has been condensed, it turns into water. A condensing boiler, on average, creates around 2 litres of condensate water per hour, and it needs somewhere to go! By having a condensate pipe, the water is safely disposed of with the rest of the waste water, just like a sink or washing machine.

Where to find it

You'll usually find your condensate pipe leaving your home at the nearest outside wall. It usually looks like a small, white pipe starting from the wall, then heading down into a drain or run off system. Condensate pipes can sometimes be connected straight into waste water flows, such as the waste pipe of a sink.

Impact of a frozen condensate pipe

During freezing winter weather conditions, it’s possible for your condensate pipe to freeze if the pipe terminates outside of your property as water is passing through the pipe. If this happens, it is most likely that your boiler will fail to start, meaning no heating or hot water.

If a frozen condensate pipe is to blame for your boiler failing to start, it means that you have to defrost the water that has built up within the pipe before it will work again.

How to prevent your condensate pipe from freezing

  • Cover your external condensate pipe with foam pipe insulation
  • During freezing weather conditions, leave your heating on overnight at a lower temperature to keep the condensate warm. Although this uses energy, your boiler will take less time to heat up your home in the morning.

How do I know if my condensate pipe is frozen?

Before attempting to thaw a frozen condensate pipe, it’s important to make sure that’s the cause of the problem. The first warning sign that your condensate pipe has frozen may be an error code on your boiler. On Vaillant boilers, you’ll get an F28 or F29 code.

Error codes on other makes of boiler may vary, but a tell-tale sign is a gurgling noise coming from the boiler.

If the boiler was working fine up until a bit of a cold snap, there’s a strong chance your issue is a frozen condensate pipe.

How to defrost your condensate pipe

Luckily, you can solve this issue yourself, without incurring call out fees from the manufacturer or a heating engineer.

  • Firstly you will need to locate where the blockage is within the pipe.  Usually, your condensate pipe will be frozen on the most exposed external point, which will normally be at the end of the pipe.
  • Once you have located the blockage, you can then begin to thaw out your condensate pipe by pouring warm water along the condensate pipe to remove the ice blockage.  Use a suitable container like a watering can and keep pouring warm (NOT HOT or BOILING) water over the length of the pipe until either the ice falls from the pipe or the contents of the pipe are fully drained.
  • Once the pipe has been defrosted, restart your boiler - following the instructions in the manufacturer's boiler manual.

Follow this easy step-by-step breakdown of the process - You can skip instruction 3, but if you do need advice, get in touch

For further advice on getting your heating system ready to serve you well during the cold winter months, get in touch, we are always happy to answer any questions you may have

☎️ Call us on: 0203 488 0883 or email: hello@bealesservices.co.uk