We have a baxi combi boiler - not sure of the precise model, anyway the pressure can range from anywhere between 1.5 - over 3.0 - BF has drained the system and it remained around 1.5 for a little while, haven't had the CH running for a few months but when I did test it the system started making a banging noise (pipes) and the pressure seemed to go up instead of down, can have washing machine and dishwasher on and it's fine other days it won't be - any ideas and suggestions would be much appreciated.