A friend of mine has a Baxi Bermuda 552 back boiler fitted behind her gas fire in her lounge. One of her radiators was leaking and has now been repaired but a lot of water was lost from the system. I cannot fathom out how to refill the system or increase the water pressure (if necessary). Does it automatically refill itself or should there be a pressure gauge and in-fill tap somewhere on the system? I have looked everywhere. Any suggestions?