Error 117

Safety precautions:

1) If you smell gas or suspect a gas leak, leave the property immediately and call the gas emergency number — do not attempt any work on the boiler. 2) Switch the boiler and thermostat off and isolate electrical power to the boiler before doing any work. 3) Allow the system and radiators to cool before touching valves or bleeding radiators. 4) Have towels/containers ready to catch water; wear gloves and eye protection if possible.

Initial checks a homeowner can do:

1) Look at the pressure gauge/display on the front of the boiler when the system is cold. A normal cold reading is around 1–1.5 bar. 2) Turn the heating on and observe how much the pressure rises. A rise of up to about 0.5 bar is normal; a rise significantly more than this suggests an expansion vessel or PRV issue. 3) Check under the boiler for the filling loop (a braided hose with valves). Ensure the valve(s) are fully closed and, if your filling loop is a temporary connection, that it has been disconnected and removed after topping up. 4) Check outside or under the boiler for a small copper discharge pipe; if this is dripping or running water it indicates the PRV is discharging.

Step-by-step diagnostic and DIY fix steps:

1) If the cold pressure is above about 2.5–3 bar, switch the central heating off and let the system cool. 2) Reduce pressure by bleeding radiators: starting with the radiator furthest from the boiler, use a radiator key to open the bleed valve slowly until air hisses out; when water appears, close the valve. Repeat until the boiler pressure gauge drops to roughly 1–1.5 bar. Take care—radiators and water may still be hot if not fully cooled. 3) After bleeding, recheck the boiler pressure when cold; if it is in the normal range, restart the heating and monitor pressure. If the 117 fault clears once pressure is reduced, the immediate issue is resolved. 4) If bleeding does not reduce pressure, or the pressure rises again quickly, check the filling loop valves: ensure they are fully closed. If the filling loop is a permanent braided hose, consider isolating and removing it if safe to do so (many installers disconnect it after topping up). If you suspect the filling loop valves are leaking even when 'closed', stop using the boiler and call an engineer. 5) If the PRV discharge pipe is dripping or has been discharging, the PRV may be faulty or the expansion vessel may be failing. Continuous discharge or frequent re-pressurising after bleeding indicates a component fault.

When to call a professional:

1) Call a Gas Safe registered heating engineer or Baxi customer support if: bleeding radiators and closing the filling loop does not cure the high pressure; the filling loop appears to be leaking when closed; the PRV is discharging water; the expansion vessel needs checking or recharging; or the boiler remains locked out with the 117 fault after you have corrected pressure. 2) Do not attempt to replace or repair the PRV or expansion vessel yourself — these are job for a qualified engineer. 3) After an engineer has corrected the fault, ask them to verify the expansion vessel charge, the PRV condition, and that the filling loop is correctly isolated or removed.

Resetting the boiler: once you have reduced system pressure to the correct level and fixed any leaking filling loop, the boiler will often clear the error itself. If the boiler is locked out, consult the manual or Baxi support for the approved reset procedure and only reset after pressure is safe. If the fault returns after reset, turn the boiler off and call a professional.