Thanks; have confirmed there is no bypass valve, but also no trv's at all. I have lifted floorboards and checked all piping is secure; any further ideas?
I have a gas central heating system that functions perfectly as far as heat is concerned. However, the two radiators at the back of the house (ground and first floor) cause a loud humming to come from the pipes nearby when they are turned on. If I reduce the flow through the radiators, the...