Set Appliance State:
Gas Off
Isolate Mains Power to appliance as per TOPs P4
Close heating flow and return valves and drain through safety valve. Remove return valve spindle guide assembly.
Close heating flow and return valves and drain through safety valve. Remove return valve spindle guide assembly.
Observation:
Examine for blockages or dirt.
Isolate as per TOPs P4
and refit as necessary