I have just a had new thermostatic shower installed, which has concealed pipework. The shower runs cold when it is on the hot setting and hot when it on the cold setting. Also, there is no warm water, it goes from boiling hot to freezing cold. The person who installed it says the shower is faulty, I was wondering if this is the case or is it possible that the inlet pipes have been reversed when fitting??? any help appreciated. Also this shower is run from a combi-boiler, we have 2 other thermostatic showers from the same boiler which run fine.