Air block noise from flush
My flush has started to make a loud noise every time it is pulled. It sounds exactly the same as the noise you hear if you had an air lock in the pipes. If you run a cold tap elsewhere in the bathroom the noise stops. As soon as the flush re-fills however if you pull it again the noise starts again!
There are no other problems in the rest of the house. The gas heating system is only two years old and all the pipes and radiators were new at this time.
Can some one suggest what the problem is?