noisy system

[greggx101]

I had a new boiler fitted a year ago - a glowworm hxi 15. Recently there has been a wooshing metallic noise that i can only describe as sounding like when you put your ear to a sea shell and hear the sea !! Its quite load. When i turn the system off it continues for aabout 5 minutes. The noise is upstairs in the pipes where they come out the floor and lead to the pump.

I discovered 3 settings on the pump , i turned it to the medium setting and the noise is somewhat quiter, however at this lower setting there is a new some awfull banging going on when the boiler first comes on for about 5 minutes so i turned the pump back to the original high setting.

Any idea what the noise is ? I turning the pump down bad ?


thanks