When ever I use the hot taps my system starts humming - any ideas?
Cheers
Wd

A humming sound=vibration. Does this happen on all your hot water faucets or just one? Is it louder on just one? Did it just start or has it been ongoing?
Back to you, Tom

It happens on all the hot water taps - It has only just started (Couple of days ago)

Have you gor heat traps in your water heater? The ball vibrating in the nipple coming out of the hot side would explain this situation. Regards, tom