have a family member with single handle shower, as you turn it-- cold and cool water come out spout, but shower will not come on til it becomes warm--is this a water pressure problem?, or normal for single handle shower, --its a new shower----I'm interested in this because I'm going to replace mine with a single handle shower( I was told yesterday that it is the code now)also I may be able to help my family member-----could it be a brand problem???