Ok it's me again, but not discussing vibration this time, but my OWN water heater. If I turn it on in the mornings and get the 2 hours of afternoon heating (economy), it's fine....but if I forget to turn it off, by about 8 - 10pm in the evening there are loud noises (as if someone is in the other room) and if I touch the copper pipe at the top of the cylinder, I can feel a gentle 'rushing' along it. I'm paranoid about explosion risk, I know it's low, but I have an 80 year old landlady and a plumber who is not very responsive to her calls for help. Weeks go by. I will of course let her know again, but meantime I'll make sure I only use the 2 hours heating in the afternoon. It's all I need anyway as the water stays hot until the following morning. But how paranoid, or not, am I being? A plumber has seen the boiler in the last year. He said something needed fixing on it to allow pressure to be released, and since he touched it, the top copper pipe gets hot...guessing that's normal? Thanks.