noisy hot water tank when boiler not on

thriftytiger

Thanks for your very helpful diagram Penrhyn, been to have another look, yes it does have an immersion heater, but this is turned off at the switch and always has been as far as I know. I couldn't find a timer, so don't think it can be coming on? We've also checked the cost of our fuel bills and they are about what you would expect (without a costly immersion heater coming on every night).

I had read elsewhere and been told that an immersion heater could be in a separate tank or in a kind of separate section of the main tank (obviously immersed in water), hence my question re a separate tank, clearly this isn't right.

I have turned off the switch to the shower pump to see if that makes a difference.

Many thanks for all your suggestions, I'll work my way through them and hopefully get to the bottom of it.