I have had a new extension built and I have had 2 new radiators added to my existing system. I have had a new boiler, pump and 2 three way valves added. All my radiators are piping hot apart from the 2 new ones which are luke warm. I have had the system balanced twice by the heating engineer who fitted the boiler and 2 new rads, without improvement. The only way to get the radiators hot is to turn all the other rads off, and then they still are not quite as hot as the others. The pipes feeding the 2 new rads are always piping hot. All my rads have had new TRV's fitted. Also my hot water is way too hot. The tank thermostat is set at 45 c but the only way to reduce the water temperature is to turn boiler temperature down, but then the rads go cool. My heating engineer says that I need to change some of my pipework leading downstairs from my hot water tank from 15mm to 22mm to give a better supply of water to the rads. Is this usual? Why have I got 2 three way valves? Can anybody help?