You need at least 50 psi, and if there is a restrictor, remove it.
It can be but shouldn't be. If its plumbed in half inch you will have a lot of issues with pressure drops and huge drops in water pressure when two taps are opened at once.Usually 20mm 3/4 is run to the shower/s and then half inch to other fixtures
An average flow rate cannot be determined as there are many different shower heads and each house in every country has different water pressure and not everyone may use full pressure when using a shower. But, approximately said that the average flow rate of shower water 2.5 gallons per minute at a water pressure of 80 pounds per square inch.
1-1/2 inch drain for above grade and 2 inch drain for below grade. Most UPC-based codes (IAPMO) require 2 inch above and below grade.
Not many. Maybe one at best. Half inch copper line is too small for most needs. 3/4 only costs a little more. You will go completely mad waiting for a bathtub to fill with half inch lines. Every flush of a toilet will make the shower die out.
At the bottom of the Mariana Trench (Pacific Ocean), where water pressure is about eight tons per square inch.
If you wish to control the second head from the original shower control, then come off the head. That way both shower heads can be controlled from one location. Realize that the water pressure will decrease as they have a common source, which is normally a 1/2 inch line.
What pressure per square inch water is. -In a typical home on city water you have a PRV set to 50-70 psi
one inch water gauge
321 pounds per square inch.
Pressure (Static) is 0.433*(H). H in feet. answer in pounds/sq inch
Depending on the time allowed, all the water you want.
2 tons for every square inch