Yes, I think you have spotted the problem. The pump needs to push water
around for the BOILER thermostat to work properly. Depending on the
boiler..it may have to high a temp..


The bypass loop itself may actually be a bit loud running full bore.
If you have adjustable pump speed on the boiler try reducing it a bit.


No adjustment of speed on the boiler pump available unfortunatley.
Should I try adjusting the automatic bypass valve on the boiler? The
noise from it can not be anything like as loud as the noise we have at
the moment (it wakes us up early in the morning and we are on the other
side of the house!)!!!! I think my question still stands about whether
it is normal practise to add another bypass in addition to the one on
the boiler??