Category - Boilers
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Ryan Gill, Engineer

31 Jan : Updated 19 Apr ● 7 min read

How to fix a frozen boiler condensate pipe

We depend most heavily on our boilers to supply our heating and hot water during the colder months of the year. The condensate pipe on our boilers, however, can become more prone to freezing as the temperature drops below zero, which could result in the boiler shutting down. 

It goes without saying that a frozen boiler condensate pipe is one of the things every homeowner, landlord, and tenant dreads. There’s no worse feeling than waking up in the morning and realising that your boiler has stopped working because of the cold weather. 

This guide will explain how to fix a frozen boiler condensate pipe, how to prevent the problem from occurring and point out factors you can look for to pinpoint a smaller problem before it turns into a much bigger one.

What is a condensate pipe?

A boiler condensate pipe is an essential component in condensing boilers, designed to manage the discharge of water produced during the condensation process. Typically constructed from plastic, this pipe facilitates the safe transportation of the condensate from the boiler to either a household drainage system or an external soakaway. Its primary function is to ensure the proper disposal of wastewater, contributing to the efficient operation of the condensing boiler system.

As you can imagine, this pipe is essential. If it freezes internally, this can cause a lot of problems and should be fixed as soon as possible. 

Where can I find a condensate pipe?

Identifying your condensing pipe should be relatively easy. It’s usually a white plastic pipe that is connected to your boiler from underneath. The white pipe should take a route from the boiler either to an internal or external drain. It should also be angled to ensure waste water doesn’t flow back into the boiler.

Condensing boilers need an extra pipe installed to remove waste water that collects in a “trap” within the boiler. This wastewater is a byproduct of burning gas within the boiler to efficient levels.

Since 2005, condensing technology in boilers has been a requirement in a bid to increase the energy efficiency of these home appliances. It means that more latent heat can be recycled within the boiler and used again to heat the water. 

What causes condensate pipes to freeze?

During the winter, outdoor condensate pipes are exposed to lower temperatures. As a result, the water in the pipe may freeze and obstruct the flow. If exposed to severe weather, portions of the pipe are susceptible to freezing. 

Because condensate water is not released when the pipe freezes, the boiler will become clogged. Which could result in the boiler malfunctioning, leaving you without heat or hot water. In order to prevent wastewater from accumulating and flooding the heat exchanger, in some cases, the boiler will lockout at this point.

The condensate pipes may freeze if the piping is not large enough, fitted at an incorrect angle, or it has been incorrectly insulated.

Is my condensate pipe frozen?

If you suspect your condensate pipe to be frozen, then ask these questions. 

  • Is the external temperature below freezing?
  • Has your boiler been working fine one day, then the next, you have no heating or hot water?
  • Can you hear a strange sound coming from your boiler? 

If so, then this is an indicator that your pipe may be frozen. Your boiler may also be able to detect a frozen pipe and, as a precaution, will prevent it from operating entirely. Most modern boilers have built-in frost protection.

Sometimes, your boiler will show a fault code to inform you of a frozen condensate pipe. Depending on your boiler, it might be any of the following: 

  • EA' fault code
  • D5' fault code
  • A blue light that flashes slowly and goes off for a longer period of time than it flashes on.

If you notice a leak on your condensate pipe, then you’ll need to talk to a professional. Take a look at our guide on whether a leaking condensate pipe is dangerous for further information. 

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How to thaw a frozen condensate pipe

There are numerous ways to thaw a frozen condensate pipe, but do approach it with caution, as you’ll be handling hot water. 

The first, most important thing to do is to locate the frozen pipe. It’s important that you don’t take drastic measures to move or remove the pipe entirely - a Gas Safe Registered engineer should be the only person to complete any physical pipe work. However there are things you can do to help fix the frozen pipe without the need for a registered professional to come to your home.

How to defrost a frozen condensate pipe

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1. Warm up some water

By using a kettle or a microwave, heat up a little water. The water shouldn’t be boiling, as this can cause further damage to your boiler pipe. The water should be at a warm enough temperature to thaw the frozen pipe a little, but not too hot as this will ruin it.

Note: By using boiling water, you run the risk of damaging the frozen condensate pipe, so make sure the water is of an optimal temperature.  

2. Pour the water over the pipe

The frozen part of the pipe should be covered with warm water. If you know where your pipe is frozen, you can target this area first. If not, you can start with the main outlet. This will help to unfreeze the pipe in different areas.

After this, you can check with your boiler whether this has been a success. 

Still having trouble with your frozen condensate pipe?

Sometimes, your pipes may be frozen beyond the level that hot water can quickly rectify the problem. Luckily, there are ways around this. 

Another thing to try is holding a hot object onto your boiler condensate pipe for longer, such as a hot water bottle, allowing the heat to be continuously applied. A trickling sound will indicate that the running water has been unfrozen.

After this, when you’re confident your frozen pipe is fixed, you can then try and reset your boiler. If it boots up as it should, you should be able to use your boiler as normal.

How to prevent your condensate pipe from freezing

If you’ve suffered because of frozen boiler pipes, then you need to take the necessary precautions to make sure it doesn’t happen again. There are two main things you can do:

1. Insulate your condensate pipe

It is best to use waterproof insulation to ensure that your pipe will not get wet and freeze once more.  By insulating your condensate pipe, you can prevent any future frozen pipes when the temperatures plummet. Further protection from freezing can be achieved using a thermal warming kit (also known as a trace heating pipe kit), which can be installed by a competent electrician or Gas Safe registered installer. 

2. Get your boiler serviced annually

There are numerous benefits to having your boiler serviced regularly, and, if your condensate pipe is frozen then having a cover plan in place could help.

With a BOXT home cover plan you can spread the cost of your annual service throughout the year. Plus, we'll let you know when your service is due, then you can choose a date that works for you and book through the BOXT App, and we'll arrange for a Gas Safe engineer to visit. 

3. Talk to a registered engineer

A Gas Safe registered engineer may be able to move the location of your condensate pipe so it’s inside a property, terminating into an internal drain or waste pipe. This means that it’s less likely to freeze.

Alternatively, they may be able to reroute the pipe or alter the angle of it to help improve water flow. 

Don’t suffer with boiler breakdown

Having a boiler breakdown is enough to put anyone into panic mode. A condensing boiler frozen pipe is something that can be easily fixed or prevented with the right knowledge. 

Follow our simple steps to fixing the issue, or, if you're finding your boiler is still running into problems, you can use our live chat to get advice from one of our qualified engineers, click to book a boiler repair visit, or if you bought your boiler from BOXT or have one of our Home Cover plans, you can report the issue here.

If your current boiler is on its last legs, we'd recommend finding a brand new one to replace it with; it can be much cheaper than constantly replacing parts. Take a look at our Find A Boiler tool to find the perfect boiler for you and your home.


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