As the sealed system does not have an expansion tank, we are looking for a screw to turn 90 degrees to let water in and repressurise the system. Please could you help us locate it and describe what should happen. We were expecting a hissing sound and the one we thought was the one did not - so we retuned it to original position quickly!

Desperate cold carer, October 2007

I believer that this migh be located on the mains cold water pipe pipe that connects to the cold water pipe pipe leading into your boiler

NM, October 2007