We have a Thorn boiler in our rented house, and a water tank in the bathroom. This has NEVER been warm to the touch. The rads come on upstairs if you select to heat the water only, now you get hot water for seconds and then it runs cold, throughout the house, yet the heating fires up fine. The tank seems old, there is no immersion switch, just a brass tap on the right hand side of the tank, on a pipe, and another, larger tap at the back. I have not touched this tap, but have tried to turn the tap nearest to the boiler, to see if that will adjust the water temperature, but nothing works. Any suggestions, please? Thanks.