Hi all. At a job today there's a regular boiler feeding an unvented cylinder, heating, hot water and UFH. For some reason the flow to the UFH was cold whilst the return was getting hot. So we swapped over the pipework hoping that was the fix. Unfortunately it wasnt. The set up has three 2 port valves which seem to work fine when the stats are operated. Anyway after swapping the flow and return from the boiler we wasn't getting much heat in the rads. Maybe the return was backing up? Any of you lads got any ideas what to look for tomorrow???