Your boiler has a condense pipe, but do you need it? (It's going to freeze)
In simple terms, the condensate pipe has an important role in removing acidic wastewater from your boiler to the drains outside of your home.
When the temperature begins to drop, it’s common for the contents of the pipe to freeze, causing a blockage and resulting in the boiler completely shutting down.
Most of the best combi boilers will have a specific error code to indicate a frozen condensate pipe, which will be displayed on the interface.
In this guide, we are going to take a deep dive into the world of condensate pipes, their function and how to deal with them when things go wrong.
First up, what actually is a condensate pipe?
The condensate pipe is a pipe that essentially transports 'condensate' wastewater from your boiler to the drains outside of your home.
Why is this important?
All modern gas boilers now recycle the latent heat from the boiler's waste exhaust gases, which results in the condensing of water vapour within the waste gases to extract the heat. This is different from old non-condensing boilers that only extracted heat from the burning of gases.
Since modern boilers are able to extract heat from waste gases, it makes them much more efficient, but it also results in the formation of condensate (water vapour) as a result of this condensing process.
This wastewater product has certain characteristics that mean it has to be dealt with in a certain way, primarily it is somewhat acidic, so needs to be transported in plastic or PVC pipes.
At high temperatures, the condensate is transported via metallic pipes e.g. aluminium, but this is usually within the boiler, the condensate pipe will usually be found coming out of the back of your boiler, down the external wall and into the drain.
As a result of this, condensate pipes are relatively easy to identify...it's the small, usually white pipe found on your external wall.
Great, now, what does a condensate pipe actually do?
As mentioned, the condensate pipes' role is to transport acidic wastewater produced during the condensing process and deposit it into the sewer.
For illustration, the typical modern condensing boiler can produce between 2 or 3 litres of condensate water waste each hour the boiler is operating.
In a similar way to the U-bend found under your kitchen sink, the condensate pipe is designed so that water is only released once the volume has hit a certain threshold.
In general, the water will be released in 300ml increments, which is why you may hear gurgling noises every so often when running your gas boiler.
The reason why the pipe releases the wastewater in increments instead of a continuous flow is to reduce the risk of the water freezing in the external pipe, which can cause a potential blockage. This is particularly helpful during the colder winter months.
Condensate pipe problems
As mentioned condensate pipes are designed to release the acidic wastewater in bursts and not all at once, this is to help prevent the risk of the pipes freezing.
However, sometimes this measure isn't enough, especially in the depths of winter when subzero temperatures are more common.
The stretch of the pipe that will freeze is almost always the section that runs outdoors or in areas where there is no heat, for example, down the external wall of your house, or in a garage or outhouse.
Not so sure if your boiler is suffering from a frozen condensate pipe? Check our comprehensive guide on common boiler problems.
How can you prevent a frozen condensate pipe?
To prevent your condensate pipe from freezing, there are a number of measures you can take, including the following:
Make sure the pipe is no longer than 3 metres from your boiler to the sewer/drain itself.
Any portion of the pipe that is exposed to the outside air should ideally be insulated.
The condensate pipe should be installed at a gradient since you don't want any backsplash from the drain to travel back up to your boiler.
Related boiler guides:
How can you tell if your condensate pipe is frozen?
In most situations of a frozen condensate pipe, you will easily be able to tell by looking at your boiler's interface.
Most modern boilers will have a specific error code for a frozen condensate pipe, which will be displayed on the interface.
Typically, the boiler will also 'lockout' and you won't be able to use it until the blockage has been dealt with.
How to fix a blocked/frozen condensate pipe
Unfortunately, a frozen condensate pipe is one of the most common boiler problems that face people in the UK, especially during winter.
Thankfully, it's a relatively easy issue to fix with some warm water.
Once you've located the outdoor section of the condensate pipe, apply hot water to the whole external section. Water between 60-70° would be ideal.
Thawing out your condensate pipe can take considerably longer than expected, sometimes several hours of repetitive effort. Don't make the assumption it's thawed out after just one application of hot water.
It's likely that you'll have to repeat this process several times and it will likely require several watering cans worth of hot water before the thawing begins to take place.
Another option is to use a hot water bottle.
If you have a hot water bottle then we would recommend first applying the hot water as mentioned above, followed by holding or securing a hot water bottle against the outside area of the pipe for as long as possible.
Applying both of these methods should greatly reduce the time it takes for the frozen condensate pipe to thaw out.
If the temperature is below -2 degrees Celsius, the hot water you pour onto your condensate pipe will freeze again very quickly.
The application of the hot water bottle will prevent this and make it much more likely for the water to thaw, quickly.
In extreme circumstances, you may have to cut the section of the pipe that is frozen.
How to prevent a condensate pipe from freezing
Once you have dealt with your frozen condensate pipe, you're probably wondering how you can prevent it from happening again in the future.
The answer is to insulate the pipe as much as possible.
Note that in very cold temperatures - wrapping the pipe alone will not be enough to thaw out the frozen condensate pipe.
You can wrap the pipe in random household items, however, most DIY stores will sell specific materials that are designed to fit snugly around your condensate pipe and provide the best insulation to prevent further freezing. These pipe covers are usually available at next to nothing.
What size condensate pipe do you need?
If you are thinking of replacing your current condensate pipe or are installing a brand new one, you'll need to know the correct size and type of pipe you'll need.
Since the condensate is slightly acidic and needs to be extracted in bursts, it's important you select a pipe that is of the correct size and made of the correct material.
So what type of pipe do you need?
The overflow pipe needs to be a minimum size of 21.5mm for internal.
The overflow pipe can be a minimum size of 32mm for external installation.
It also needs to be made from plastic such as PVC, since the contents will be slightly acidic.
You also need to consider the installation position of the condensate pipe.
It should be positioned and installed on the wall in such a way to help the contents gradually flow down to the sewer/drain. That means a minimum decline of 44mm per metre.
What if you don't have a drain?
If you don't have a drain to lead the condensate pipe to, the solution is to use an innovative product called 'soakaway'.
As the name indicates, this product is designed to absorb the condensate, which it does by the use of limescale chippings, which are also able to quench and neutralise the acidic content of the wastewater.
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