I have a tank that sits on top of my cold water storage tank in the attic - I presume this is the "expansion tank"?
This feeds the heating system?
Just that there is no over-flow pipe on it. There is a mains pipe feeding it with a ball cock. I'm afraid if the ball cock fails.
Why would any numb-skull not put on an overflow pipe?
It is smaller than the tank underneath but it means then that I can't cover it, plus it sits on two planks so if it overflowed it wouldn't go into the tank below.
I suppose it's the same as any toilet to which an overflow has not been fitted, but it's worrying when it's in your attic, looks like it could destroy the house, particularly as the expansion tank is metal (not plastic) and it looks like it has been there for 50 years....