Hot water coming out of cold taps!

[Nino]

Hello

This is my first post here so I hope I can find some help with my problem.

When we switch our central heating and water on, after a while hot water starts coming out of the main cold tank overflow pipe in the loft in a heavy stream. Then when we switch the heating off the overfolw from the cold tank stops but the overflow from the feed and expansion tank starts flowing. Recently we had the strangre thing of really hot water coming out of the cold taps and toilet upstairs.

Any thoughts as to what this could be?

Cheers
Nino

 

[Nige F]

The heat transfer coil inside the hot water cylinder could be leaking....water from heating system getting into domestic hot water and vice versa