This morning (5/10/03) i finally succumbed and put my central heating on. The hot water has been working fine all through the summer but when I turned the thermostat up to 20 degrees to bring the radiators to life, they warmed up for about 5 minutes then went cold again. On further investigation i found a slight rumbling sound coming from all of the radiators in the house but no hot water at all was being fed to any of them through the pipes ( the pipes leading to and from each one felt stone cold). I guess something was working as my water is extremely hot but wonder if you have any ideas as to why no hot water is getting to the rads?