Category - Boilers
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Will Scholfield, Engineer

23 Nov : Updated 26 Mar ● 6 min read

Is a leaking condensate pipe dangerous?

Leaks and boilers aren't exactly the best of friends. Whether it's a leak from your hot water cylinder, your radiators, or any of the connecting pipework, leaks can be a sign of a serious fault somewhere in your central heating system.

And, more often than not, faults lead to frustration, so it's natural for anyone experiencing issues with their boiler to want to get things fixed as promptly as possible. That's why BOXT's team of boiler engineers have put together this guide to walk you through the possible causes behind a leaky condensate pipe and why, in some cases, a leak could end up proving dangerous.

Common reasons for leaking condensate pipes

There are a few reasons your condensate pipe might be leaking. We'll go through each of the possible scenarios and how to fix them, whether you can do it by yourself or need to call a heating engineer.

Split or corroded heat exchanger

If your boiler condensate pipe is dripping, it could be due to a split or corroded heat exchanger. The heat exchanger's job is to take the heat from the burnt gases and use these to heat the water contained within it. This hot water then is used to supply either your radiators or hot water outlets.

The plastic material of your condensate pipe is designed to withstand the acidity levels in condensate water. But it's not designed to withstand the high temperature of the water within the boiler's heat exchanger, so if this does become compromised it could cause the joints to start leaking or break entirely.

If this happens, it is not something you can fix yourself, and you'll have to contact a Gas Safe registered engineer. You can easily book a repair visit from BOXT or, if you're an existing BOXT customer, report the problem and our expert team will be in touch to get it sorted.

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Condensate pipe joint leaks

Condensate pipe joint leaks can happen because of the heat exchanger issues mentioned above, but that's not the only cause. It can also happen if the pipe and joint were incorrectly installed.

If the condensate pipe was incorrectly installed, you may notice:

  • The joints are not properly sealed with PVC pipe cement.
  • The incorrect pipe and fittings have been used (not plastic or PVC, or the right diameter).
  • The fittings have metal content (they will erode).

If the problem seems to be the lack of PVC cement on the joints, you should be able to fix the issue yourself with some store-bought PVC pipe cement. 

If installers used the wrong pipes and fittings, it's best to contact a professional engineer who’ll have the skills and experience needed to get the job done correctly. 

Condensate trap blockage

Your boiler's condensate trap is responsible for safely collecting and releasing condensate wastewater as well as forming a barrier stopping products of combustion from entering the condensate pipe. Over time, sediment can collect and build up. If you can hear a gurgling noise coming from the exhaust end of the flue, that's potentially a sign of a blocked trap or pipe

If you suspect a clogged condensate pipe trap is to blame for your boiler failing, you should contact an engineer rather than trying to fix the problem yourself, as the job requires a Gas Safe registered expert.

Luckily, rectifying the issue shouldn’t take more than an hour or two, meaning it’s typically a fairly inexpensive job. Your heating engineer will clean the trap by removing it, rinsing it out thoroughly, refilling it, and refitting it. This issue can be minimised by having an annual service and maintenance inspection carried out on your boiler.

Condensate pipe blockage

This is a very similar problem to the one above. The main difference is that it's the pipe itself that's blocked, rather than the trap. The most common cause is water freezing in the pipe, but it can also be blocked by other debris.

Read our expert’s dedicated guide for more advice on how to fix a frozen boiler condensate pipe.

Why is a leaking condensate pipe dangerous?

There are several reasons why a leaking condensate pipe could be dangerous if left unfixed. Don’t worry, though; you’ve come to the right place. Let’s take a look at the mechanics of why a leaky condensate pipe can end up compromising the efficiency and overall functionality of your boiler.

Acidic water

The wastewater that travels through your condensate pipe is slightly acidic. That's why the condensate pipe is made from plastic or PVC instead of metal so it doesn't corrode over time. Now, although any leaking water in your home is far from ideal and probably something you’ll want to get sorted out as soon as possible, leaking condensate can prove far more than just an annoyance.

If condensate is allowed to leak onto any metal components connected to your boiler, such as the gas pipe, it will end up causing corrosion. We don’t need to spell out the significance of this; damaged gas pipes lead to gas leaks which, in some cases, lead to gas explosions.

What’s more, if condensate is leaking onto any electrics - wires, PCBs, fuses and so on - it can cause things to short-circuit. Even for gas boilers, this can result in system failure since gas appliances need electricity to ignite and operate efficiently.

Risk of further damage

If the leak is in the portion of your condensate pipe that's outside your home, there is a greater risk of further damage being caused to the pipe. In winter in the UK, condensate pipes are susceptible to freezing anyway. If there's a leak while temperatures are low, the frozen water will expand in the gap and make the leak worse.

Quality of life

Your boiler is an essential part of your home, especially during the cold winter months when it's responsible for providing you with a much-needed hot shower and a comfortable, warm home to relax in. If you have condensate water leaking inside your home, your boiler could stop working altogether.

If you find yourself without central heating in winter (or, as we’re in the UK, during a cold snap in spring or autumn), this could prove dangerous by causing a whole host of health problems, increasing the risk of heart attacks and strokes and worsening respiratory conditions like asthma and COPD. This isn’t merely a scaremongering tactic but something that is backed up by extensive research carried out by Public Health England and the UCL Institute of Health Equity.

For safety reasons, it’s important that you fix the leak as soon as you spot it or, if in doubt, contact one of BOXT’s professional engineers.

Need help with a leaking condensate pipe? Talk to BOXT

A pipe leaking anywhere in the house will cause you stress, whether it’s dangerous or not. If you’re in any doubt about the root cause of a leak, don’t hesitate to contact the professionals for support. Speak with someone from our friendly team of engineers for free, no-obligation advice via the live chat or book a repair visit to bring the help straight to your home.