Heating 4 min read9 March 2026
Every cold snap in Glasgow brings a wave of identical calls: the boiler was fine last night and this morning it is locked out with a gurgling noise. Nine times in ten it is a frozen condensate pipe.
How to thaw it safely
Locate the plastic pipe running from the boiler to an outside drain. Pour warm — not boiling — water along its length, concentrating on bends and the open end. Boiling water can crack the pipe. Once cleared, reset the boiler using the manufacturer's reset button.
Stopping it happening again
A permanent fix means upgrading the pipe to a larger diameter, re-routing it internally to an existing waste where possible, improving the fall, and lagging any external run with weatherproof insulation. That is a short job and it removes the problem for good.
When to call an engineer
If the boiler will not reset after the pipe is clear, if it locks out again within hours, or if you cannot safely reach the pipe, call us. Repeated lockouts can point to a blocked condensate trap inside the appliance rather than ice outside.
Need help with this?
We handle this work every week. See Heating & Boiler Services in Glasgow or browse all our services.
Frequently asked questions
Can I use boiling water?
No. Use warm water — boiling water risks cracking the plastic pipe or damaging fittings.
Is a frozen condensate dangerous?
The boiler shuts down safely, but you lose heating and hot water until it is cleared.
Can you reroute the pipe internally?
In most properties, yes — it is the most reliable long-term fix.
Related reading
Boiler Repair in Glasgow: 10 Faults We Fix Every Week
Why Your Boiler Keeps Losing Pressure
Burst Pipe: The First Five Minutes Matter