So today I just had seven Trent out to test water pressure to see if water hammer type noises is caused by it ! But only came back as 4.01 bar which they say is well within there limits ! Problem started off with small knocking when washing machine stopped started ie valve closing, but now it happens when toilets finish filling and even when the neighbour uses water now ! The noise can only be explained as breaking wind or when you pull your chair away and makes a thunder sound only short lasting no more than one second ! We get it regular in the morning when it's quiet we can hear water flow so we no when it's going to happen, any suggestions .