Potterton Kingfisher - clicking/surging noise

[carlsbergy]

When the room has reached temperature and boiler clicks off or when water reached temperature and boiler clicks off, the boiler makes a clicking noise/surging noise, then when temperature in room calls for heat boiler fires up fine and runs ok. Any ideas on clicking noise?

Also want to put it under British gas contract and the engineer on his work sheet refusal notice said something about not enough 22mm pip running from flow and return before becoming 15mm, is there a recommended length of 22mm pipe before it goes down to 15mm?

Also there is no air vent on the hotwater tank. Do I just cut into the top pipe and fit of the tank where the boiler water flows in, once system drained?

Thanks

 

[gasandoilman]

Dont just cut the pipe
get a good plumber and dont call british gas