Problem with immersion heater - i think

[AnonymousImport]

We only moved into our house about 1 year ago(the house is around 6 years old) so we dont really know much.....and arent really DIY enthusiasts.

Since last Thursday the immersion heater and a pipe that leads up from it has been making a humming sound(like it does when the heating/hot water is on) but the timer is off....only this morning we noticed water running out of the overflow pipe from the attic ...... sorry im not very clear on my explanation

 

[AnonymousImport]

It appears that you have a leaking valve. in the immersion heater cold water tank is a ball valve, this is either separate from the immersion heater tank or combined. within this valve is a tiny washer which when the water level is correct shuts of the supply to the tank. if this tiny washer fails then water continues to flow and then comes out of the overflow pipe, and vibration can happen. it is simple to replace the washer and costs just a few pence. but make sure you turn the water off before doing anything.