Help. I am in the process of refitting my bathroom. All I have at the moment is a shower. The water pipes to the sink, bath and toilet have been capped temporarily. When I switch the shower on it is almost cold unless I reduce the cold water flow into the bathroom on the isolator valve and then it is just about warm enough unless I completely stop the cold in which case the hot water is unbearable as it should be. I have stripped the shower and can not find any blockages on the hot feed, the hot pipe into the shower is red hot even when cold is flowing. I have a combi boiler. The question is, is there a problem with the thermostat on the shower or is it a pipe problem. I have moved some of the water pipes around so wondering if there is an air lock possibly. Prior to capping off everything was fine. Hot water everywhere else in the house is fine.