Condensate Trap/System Blocked
The condensate drainage system is blocked. This can occur when the condensate siphon is full after the boiler has been unused, or when the external pipe is frozen.
E113 in winter is most commonly a frozen condensate pipe. Thaw and wait for the boiler to self-clear.
Step-by-Step Fix Guide
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Step 1
In cold weather, check the external condensate pipe for freezing and thaw with warm water
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Step 2
Allow the boiler to run at low burn for 15 minutes to fill the siphon (this is normal start-up behaviour)
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Step 3
If the boiler continues to show E113, call a Gas Safe engineer to clean the condensate trap
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.