Hi does anyone have any ideas as to why my heating system is making a noise, the noise i think is the water flowing through the system but can only hear it on 3 or 4 rads. the sytem is brand new only been fitted a couple of weeks the boiler is a worcester bosch 35cdi running 13 rads on three floors the boiler being on the ground floor the supply and return pipes are 22mm with the rads being fed by 15mm all copper, all the rads have trvs fitted but the one in the bathroom is fully open all the time, i have bled the rads on a number of occasions with very little air in system the pressure is set at 1bar on the boiler i have tried to get the guy who installed the boiler to look at it but he does not return my calls so any help would be much appreciated thank you.