When my hot water heats up there is an amazing amount of banging and clanging through the house. This happens randomly until the hot water goes off. I had a plumber out who changed the ball valve but still keeps doing it, unfortunately when the plumber was round it didn't make a sound!!!! Someone else was talking about a hammer? something?...I am a female and unfort have absolutely no idea about plumbing, also I would like an idea of what it could be as I don't want to have to keep paying call out charges each time.