I have a question regarding increasing water volume in a residential plumbing installation.

My situation.
I am plumbing 2 bathrooms, the master bath (9 Cold FU, 60' from source and 6 Hot FU, 20' from source) and the second floor bath (7 Cold FU and 4 Hot FU, same distance from source.) 46 to 60 psi.

The shower in the master bath is on the same wall as the toilet and double sinks for the second floor bath. I was going to feed both bathrooms with a 1" for the cold water and 3/4" for the hot water wich according to the code is okay however I am worried about two possible problems.

1. I think there will be a major pressure drop once the water is on for say the shower and someone flushes the toilet.
2. The hot water will need to run for a while before the hot water reaches any of these baths.

So here is what I am thinking of doing and please let me know if you are in agreement.

For the pressure drop I was going to run a 1" pipe for each bathroom's cold water and a 3/4" pipe for each bathroom's hot water. Possibly use 1-1/4" pipe as a header and feed the fixtures off this header with 1/2".

For the hot water I am thinking of tying in the farthest hot water pipe to a gravity loop system back to the hot water heater's drain valve port. This should at least keep the hot water flowing to minimize time.

Your help is most appreciated and I thank you in advance.

Joe