I have purchased a bungalow with a Ravenheat LS 80 Silver Star combination boiler that is now 4 months over warantee. The system is very effective in that the hot water and central heating work quickly and effeciently and i also have a very good power shower. However, there is a very loud "rushing water" sound emmitting through the radiators when the central heating is on (it's the sort of sound you hear when you put a sea shell to your ear but it is excessive). Does anyone have any idea how i can quieten this very annoying noise?