Why the condensate pipe freezes
Modern condensing boilers produce a small amount of acidic waste water (condensate) that drains via a plastic pipe, often through an outside wall. When the pipe runs externally, tight bends collect water and freeze first.
How to thaw it — step by step
1. Locate the pipe — usually a white or grey plastic pipe running down an outside wall or into a drain.
2. Feel along its length for the frozen section (often at the base near an elbow).
3. Pour warm — NOT boiling — water over the pipe, or wrap a hot water bottle around it. Never use a naked flame.
4. Once thawed, reset the boiler using the reset button. It should fire back up within a minute.
5. Insulate the pipe with lagging (£10 from any DIY shop) to prevent recurrence.
Permanent fixes
Re-route the pipe internally so it terminates at an internal drain — the manufacturer-preferred solution. Fit trace heating cable that warms the pipe below 3°C. Upsize the external run to 32mm+. All are day jobs we can quote on.
Frozen boiler you can't thaw? Book an urgent callout across KT/TW.
Call 07932 898534Frequently asked questions
Why did my pipe freeze this year but never before?
Sub-zero temperatures below –3°C for several consecutive hours are usually the trigger. Wind chill worsens it. If you're seeing it repeatedly, permanent re-routing is the fix.
Is a frozen condensate dangerous?
No — the boiler locks out safely. But you have no heating or hot water until it's thawed.
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