Piping for water supply

Hi

I have 2 bathrooms the main one in the 1st floor and a 2nd in the basement.
I am trying to figure out how to run my supply lines.

I have a 3/4" water main coming in the house and 3/4" out from the water meter.

CURRENT configureation: From the water meter, it runs and then T off to a 1/2" pipe and the 1st T branch off the 1/2" pipe is to the main bathroom vanity sink, then it continues and T branch off to the entire basement bathroom (2nd bathroom), continues and T branch to the main bathroom toilet and then ends at main bathroom tub.

I never used the basement bathroom because it was a nasty bathroom. But now it is demolished. I never knew how the water pressure were if both bathrooms were running at the same time.

My question is by running it this way, would i have substantial lowered water pressure if I was to use the showers in both the bathrooms at the same time? Or If someones flushes in the basement would it affect someone showering in the main bathroom? Would i need to tap off the 3/4" pipe for the basement bathroom? If I can I would like to avoid doing that and using the current pipe runs, but if its' going to cause me trouble in the future, I will tap off (I am assuming) the 3/4" pipe from the water meter, to the basement bathroom.

I am also wondering about my hot water, its' run in a similar way - but obviously without going to the toilet and it originates from the water heater.

Thanks

Water Pipe Sizing

Generally, you want 3/4" to the bathroom, then reduce to 1/2" to each fixture. If you are planning a large soaking tub or a multi-head shower, running 3/4" all the way there rather than dropping to 1/2" is a good idea, but the control valves are more expensive (but can flow as much as twice as much water). Most applications can get away with a 1/2" valve, but you still often want 3/4" coming into the area.

From the Hot water heater, there is a 3/4" pipe that latter got reduced to a 1/2" pipe, could i reverse it back to a 3/4" or do i need to take out the 1/2" portion and run the 3/4 to the bathroom?

Thanks

If you are trying to address water pressure issues, you need to keep it 3/4" for the whole run (from main entering house to hot water heater to bathroom group. You should generally only reduce to 1/2" to serve a single fixture (i.e. one sink, not the whole bathroom).