I have great water pressure in my house - EXCEPT to one shower on the main level. After following the pipes below to trace the issue - here is what I found. I have 1" copper pipe from the main shut off to the water heater. From there I have 1" copper to an area where it splits off to the different levels. From there - it sizes down to 1/2" copper (for about 2 feet)- and back to 1" galvanized pipe. I'm thinking about replacing the galvanized (maybe rusted?) but I don't understand why they put in the 1/2" copper. Could that be my problem?