We have a client who called us. They have anew home with a Gas combo heating system. The floor heating only heats the basement of their new home. The hot water has a very fowl smell. It does not smell like hydrogen sulfide, but it is kind of a sweet, mild petroleum odour. No odour is noticed in the cold water. The odour does seem to dissapate after a while. Any suggestions on what the cause could be and how to solve this issue would be greatly appreciated.