Why is your boiler condensate pipe leaking?

Is your boiler leaking from the condensate pipe?

Here’s what might be causing the issue, and how to fix it safely.

Quick summary

Why is my boiler condensate pipe leaking?

• Faulty heat exchanger: cracks or corrosion can cause internal leaks.
• Blocked condensate trap: debris can build up and stop water draining.
• Leaking pipe joints: poor installation or missing sealant may be to blame.
• Frozen or blocked pipe: often caused by cold weather or external damage.

If you’re unsure or the leak continues after basic checks, call a Gas Safe engineer to prevent further damage.

What is a boiler condensate pipe?

A boiler condensate pipe carries acidic wastewater from your boiler to an external drain. This liquid is formed when flue gases from the heating process cool and condense inside the system.

Condensate disposal is a normal part of how modern condensing boilers work, but if the pipe leaks or freezes, it can interrupt your heating system.

What causes a leaking boiler condensate pipe?

If you’ve noticed your boiler condensate pipe is leaking and you’re not sure why, here are some simple troubleshooting tips you can follow to investigate the problem.

If you’ve tried these solutions and you’re still bothered by your condensate pipe leaking, we recommend calling a Gas Safe engineer to avoid making the leak worse and potentially breaking the heating system.

Faulty heat exchanger

If you’ve noticed your condensate pipe dripping, it may be due to problems with the heat exchanger.

The heat exchanger transfers heat inside your boiler. If it’s cracked or corroded, it may cause internal leaks, including through the condensate pipe.

Suppose the heat exchanger is split, corroded or dealing with limescale buildup. In that case, this can result in a faulty heating system that fails to work effectively, and in severe cases, can even lead to carbon monoxide leaks.

Any broken heat exchanger should only ever be dealt with by a professional engineer. If you notice gurgling noises, heating issues or if you think you may have a leaking heat exchanger, contact a Gas Safe engineer immediately – call our team now on 01294 468113.

Blocked boiler condensate trap

The boiler condensate trap is responsible for collecting and storing the condensate until it’s ready to be expelled via the pipe. This method of storing before discharging the condensate reduces the risk of any water freezing and causing a frozen condensate pipe.

A condensate trap blockage can sometimes be identified by a gurgling noise coming from your boiler or from the exhaust end of the flue. If debris builds and the condensate trap ever becomes blocked, it’s crucial to clear this as soon as possible to prevent potential freezing or burner lockout faults.

Clearing the condensate trap can only be performed by a Gassafe registered engineer, as they are inside your boiler. The best steps to take will depend on your boiler system, as most boilers will differ – we always advise that a qualified Gas Safe engineer deals with any blocked condensate traps.

Why is there gurgling coming from my boiler?

Gurgling sounds often mean your condensate trap or pipe is blocked. This can restrict air flow and cause your boiler to behave erratically or shut down. Call a Gas Safe engineer if the sound persists.

Condensate pipe joint leaks

Condensate pipe joint leaks can occur if the pipe was incorrectly installed, if the pipes are ageing, or from being subject to abnormal cold weather or high temperatures.

A common issue can be a lack of PVC pipe cement present to seal the condensate pipe joints. This will normally require the leaking joints to be replaced by an engineer. If the incorrect pipe and fittings have been used, an engineer may need to provide assistance. If materials other than PVC pipe cement or plastic have been used, it’s best to contact a Gas Safe engineer who will have the skills and experience to provide a solution.

Can I use silicone sealant on a leaking boiler pipe?

Silicone sealant isn’t ideal for fixing leaking condensate pipes. It doesn’t bond as reliably as PVC pipe cement and may fail over time. For a secure fix, use the correct material or consult a Gas Safe engineer.

Frozen or blocked pipe

A blocked boiler condensate pipe can lead to inefficiencies in the condensing process, causing further issues and potential damage to internal components of the heating system.

A condensate pipe can become blocked if there’s frozen water inside the pipe, which can then lead to blockages that cause a leakage upstream.

A simple fix for this is to place a towel soaked with warm water onto the pipe to clear any condensate that’s frozen inside – be sure to avoid boiling hot water, as this could damage the condensate pipe. Following this, carefully inspect the condensate pipe, fittings and joints for any breakages or splits.

If your condensate pipe frequently freezes or leaks, it may be a sign your system needs upgrading — our boiler installation team can advise on the best options for your home.

Should I turn off my boiler if the condensate pipe is leaking?

If the leak is severe or you suspect internal damage, it’s best to turn off the boiler and call a professional. Even with minor drips, switching off the system can prevent further complications.

Is a leaking condensate pipe dangerous?

Not usually, but it can cause damage if left untreated. Condensate water is mildly acidic and may corrode surfaces like the boiler chassis, skirting boards, flooring, or insulation. Fixing the issue promptly prevents long-term damage and avoids further system issues.

When should I call an engineer?

Call a professional if:

• You suspect a faulty heat exchanger
• You can’t safely clear a blockage
• Leaks persist after applying DIY fixes

James Frew’s Gas Safe engineers are on hand to diagnose and fix the issue safely.

Why choose James Frew?

We’re not just another heating company. We’ve been part of the local community for over a century, helping homeowners like you stay warm, safe and comfortable.

• Trusted across Scotland for 100+ years
• Gas Safe engineers and Worcester Bosch partners
• 4.6-star rating on Google
• 0% finance and flexible payment options

Need help with a leaking condensate pipe? Phone Frew.

If you’ve tried our tips above and you’re still struggling with leaking pipes, James Frew’s team of heating engineers can help. We’re experienced in a wide range of modern boilers and condensing technology, and can offer Gas Safe-registered expert help to keep your home warm.

Call us on 01294 468113 or complete our online enquiry form now.