If you are saying that the entire house is piped with 1/2" water lines, then you already have a major problem.
: I'm in the process of a master bath remodel,I'm installing a shower system with 3 body sprays,
: 1)handheld and 1 shower head. This would presently be supplied by 1/2 H&C. Question, should I make the H&C water supply 3/4 (to increase volume). I have a 3/4 cold water manifold in the bath, but would have to repipe the 3/4 hot, back to the water heater and place a tee in line with the original 1/2(hot) to feed the rest of the house. Would this be the proper way to install this? would I need some sort of valve at the tee? and how would this affect the rest of the fixtures?