Ignition Failure / Frozen Condensate
The boiler has failed to ignite or there is a gas supply fault. In winter, this is most commonly caused by a frozen condensate pipe.
E133 in winter almost always means a frozen condensate pipe. Locate the white plastic pipe on the outside wall and thaw with warm water.
Step-by-Step Fix Guide
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Step 1
Check other gas appliances in the home are working
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Step 2
In cold weather, check if the condensate pipe is frozen — this is the most common winter cause
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Step 3
Thaw the condensate pipe with warm water poured along its length
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Step 4
Reset the boiler once
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Step 5
If the fault persists, check the gas supply is fully open at the meter
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Step 6
If still faulting, call a Gas Safe engineer to inspect the ignition electrodes and gas valve
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.