Humming noise from water tank or boiler?

almost certainly you need new ball valve on hot water feed tank and or toilet tank though if lucky turn down incoming main pressure may cure for a while but you will need eventually

bluebird4211
April 2008

It sounds like your loo has a gravity water feed from the loft tank (not the usual way to do it, these days) - no connection with the boiler as the water isn't heated. Nip into the loft, get someone to flush the loo and see if your diagnosis is correct. Probably the fill valve washer needs replacing - I guess its bouncing a bit. The hot taps will draw from the same tank probably - the tank is responsible for feeding the copper cylinder with cold water, ready for it to be heated.

John
April 2008