Boiler
118
Error code 118 on a Potterton boiler indicates a fault with the gas valve or gas supply, meaning your boiler has shut down as a safety precaution. This is a serious fault — do not attempt to repair the gas valve yourself.
What does this error mean?
The 118 error code signals that the boiler’s control board has detected a problem with the gas valve circuit — either the valve isn’t opening correctly, isn’t receiving the right signal, or there’s an issue with gas pressure reaching the burner. The boiler locks out to prevent unburnt gas from building up. This is a built-in safety lockout, not a glitch you can simply reset your way out of permanently.
Est. repair cost
£200–£400 for gas valve replacement; £150–£350 for PCB fault — all require a Gas Safe registered engineer
🔍 Likely causes
🛠️ Step-by-step fix
Check your gas supply: Make sure other gas appliances in your home (hob, fire) are working. If they’re not, call your gas supplier — the issue is with the mains supply, not the boiler.
Check your gas meter: Ensure the emergency control valve (the handle inline with the pipe = open, across = closed) is fully open.
Perform a boiler reset: Press and hold the reset button on your Potterton boiler for 3–5 seconds. If it fires up and stays on, monitor closely. If it locks out again within a short period, the fault is mechanical — stop here.
Do NOT attempt to inspect, adjust, or replace the gas valve yourself. Gas valve work is legally restricted to Gas Safe registered engineers in the UK.
Call a Gas Safe registered engineer and quote error code 118 so they arrive prepared with the likely parts needed.
📞 When to call a professional
If the boiler relocks out after a reset, or if no other gas appliances are working, call a Gas Safe registered engineer immediately — do not attempt further DIY. Tell the engineer you have a Potterton error code 118 and whether other gas appliances are affected, as this helps them diagnose a gas valve fault versus a wider supply issue. If you smell gas at any point, do not reset the boiler — leave the property, open windows, and call the National Gas Emergency Service on 0800 111 999.
⚖️ Repair or replace?
A gas valve replacement on a Potterton boiler typically costs £200–£400 including parts and labour from a Gas Safe engineer; a PCB repair or replacement runs £150–£350. If your boiler is over 10 years old and facing a repair bill above £300, it’s worth comparing that against a new A-rated boiler (typically £1,500–£2,500 installed), which will also cut your energy bills. For boilers under 8 years old in otherwise good condition, repair is almost always the better value choice.