Forgive but I dont understand plumbing. I have a combi boiler and in my bathroom I have a non thermostatic shower mixer fitted. Its only 18 months old. I noticed yesterday that the shower would not run hot, so while the shower was running I went down to see if the boiler was on. It hadnt started automatically as it should. I then stopped the shower and started the bathroom tap, I heard the boiler flip on and I got hot water from the tap. the same for the kitchen tap etc. I really want some advice on as to wether I have a broken shower mixer or broken boiler? logically to me it sounds like my mixer isnt working properly in requesting hot water - does this make sense or are there many more complications to consider?