Have had this for about 6 years with no problem. For 1 year it has not worked. We had all the other radiators changed, then changed the valve on the towel rail, took it off and flushed it but nothing. Clear water came out of the valve when it was removed. The was a lot of black rubbish in the towel rail but it has been flushed until it is clear. Also tried turning all the other radiators off. Any suggestions.