My cold water storage tank which feeds the hot water tank keeps overflowing?

my hot water tank is pushing water up into the cold tank have got coal c. h and when the the water gets hot and the heating is not on the water overflows

PAM
February 2012

It could be that the coil from your central heating boiler that heats the hot water cylinder has failed inside the cylinder. Have a look at the heating top up tank - its usually a smaller tank, about 10 gallons, installed in your loft. Is the ball valve running constantly? It has to be higher than the cylinder so it has more pressure than the hot water system. If the coil has gone it will fill the hot water tank with water - (Water finding its own level). If it is this then a new cylinder is your only option.

Gazza
February 2007