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Last updated: 4th April, 2024


What Is A Condensate Pipe?

What Is A Condensate Pipe?

The condensate pipe allows water to be safely drained away from your home, let's drill into the details.

If you’re not currently clued up on the intricacies of boilers and some of the technical sounding component names, fear not, that’s what we’re here for.

At iHeat we’re experts in anything related to home heating, and in this blog we will be exploring the role of a condensate pipe, including how it works, potential faults and manageable fixes. 

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What Is A Condensate Pipe?

Fundamentally, a condensate pipe transfers wastewater (condensate) from the boiler to the outside of your home, with it eventually being deposited into the sewer.

What Is Condensate?

Condensate is the term for the wastewater byproduct from the central heating and hot water production process within a boiler.

When a boiler burns fuel, carbon dioxide and water vapours are released, after enough heat is produced from the vapour it’s condensed back into water, this is then collected and subsequently expelled via the condensate pipe.

Condensate water is acidic and therefore must be transported in plastic or PVC piping (at high temperatures - aluminium piping within the boiler). The condensate pipe can be found coming out of the back of your boiler, running along the exterior property wall and finally into the drain.

How Do Condensate Pipes Work?

A standard modern gas condensing boiler can produce typically anywhere between 2-3 litres of condensate waste for every hour the boiler is functioning. 

A condensate pipe is designed to release water once the volume hits a certain threshold. Usually being released in 300ml increments (often the reason you may hear water transportation through the pipes when your boiler is operational).

The reasoning behind the incremental condensate release rather than a continuous flow is to reduce the risk of the water freezing in the outside part of the pipe, which would cause a system blockage.

Signs of a frozen condensate pipe

The vast majority of modern boilers have an error code which is displayed on its user interface in the event of a frozen condensate pipe, other signs include a gurgling noise coming from the boiler or piping and the boiler being ‘locked out’ from standard use.

How To Fix A Frozen Condensate Pipe

The most common way to thaw out a frozen part of the condensate pipe, is to pour warm water over the outside of the piping, but be careful as not to cause a slip hazard.

Alternatively, you can place a hot water bottle on the affected area or have the above ground part of the piping lagged (insulated).

How To Prevent A Condensate Pipe Freezing

While many modern combi boilers have integrated frost technology to combat this there are some other methods of prevention and ways to resolve the problem if it should occur.

Firstly, make sure the pipe is no longer than 3 metres from your boiler to the drain it deposits wastewater into, also the piping should be installed at a gradient to prevent any back flow of condensate. Any exterior pipe should also be insulated to garner the best results.

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Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.