how 2 get better water pressure upstairs in a house?

Answer 1

if you have good pressure downstairs it should be good upstairs, check the aerators on the sink faucetts and remove the flow restrictors in the shower heads, without replumbing your whole house you could install a booster pump on the lines

Answer 2

Rather than looking upstairs, start by looking at the main water supply line coming from your well or city water. This is the line inside your house and is often undersized. Often, you will find that this is a 1/2" line and increasing this to 3/4" makes a big difference. Increasing the diameter will allow you to flow greater volume which should greatly help the pressure coming out of your low flow faucets and nozzles.

Answer 3

Splice in smaller water lines from the supply lines that go up stairs. that will reduce the area for the water volume and create more pressure.