we have a hot water system that seems to have its own secret water supply! hot water cylinder is in a cupboard on the first floor, with a header tank in the attic directly above it. The problem is that warm water is backing from the hot water cylinder,up to the header tank. Although this in itself is annoying, as the over flow is directly outside my bedroom window, it is not the main problem. I have drained the header tank, and turned off the mains supply to it, and turned off the boiler.... the water is still backing up from the cylinder, filling the header tank and overflowing. I have just now turned of the mains to the house, I thought; there is no water coming in for the taps or the loo cysterns, yet, yet, water is still backing up back to the header tank from the cylinder! Is it likely that the hot water cylinder is fed from any where other than the header tank, since in normal times, as we use water, the ball cock in the header tank allows it to refill?
incedentally we have a condensing boiler which is serviced every year, and was passed as good, last week. I don't get it!