Hello, I have 3/4 inch galvanized pipe into my house, It goes into a T with a 3/4 and 1/2 and 1/2. One 1/2 copper then goes to a outside hose bib, the other 1/2 copper goes to kitchen sink and then to a soft water unit. From there it goes into a water heater. From the water heater out it separates to three sinks and two toilets, washer and bath, all on 1/2inch copper pipe. I want to get more volume/pressure to my bath. I will run 3/4 inch pex from the three way to the water heater. My question is, will I need to replace the 1/2 inch copper all the way to and including the bath/shower valve?