You can not measure the pressure in a swimming pool. If you mean the pressure on the filter tank gage then you may have to backwash the filter. Talk to your local pool store for instructions as how to maintain a swimming pool and the equipment. Get some education on swimming pool maint. before you get into some real trouble. A pool is not too forgiving for someone without a basic knowledge of pools.
It lowers PH
Pressure inside Earth increases much like pressure in the swimming pool increases.
You have to know what you are doing. The addition of muriatic acid lowers the pH and total alkalinity in swimming pools.
It is not possible to have a pressure level on your swimming pool! However the pressure on the filter gage could run anywhere from 5# to 35#
A person can go to a plane after swimming in a 2M deep pool because the pressure is not too much.
the hydrostatic valve is only to equalize pressure of ground water to that of the pool the only time it does anything is when the water table becomes higher in the ground water than in the swimming pool . it doesn't connect to anything. it is simply to keep the pool shell from floating out of the ground
A Hydrostatic valve is basically a plug that stop water coming down out of the pool, but when the water pressure under the pool gets higher then the pressure in the pool it will let water into the pool from underneath in order to stop the pool from floating in ground water.
Friction
2 meters below the surface
No specified pressure at the "return" fittings at pool side. You do not measure pressure at these points.
A "relief valve" can only be accessed when the pool is empty, and no swimming pool should ever be left empty. The only exception is when absolutely necessary due to repair or resurfacing, and that should be completed within the shortest possible time. Any pool that is empty, and that has a relief valve, should have the valve removed for the entire time, regardless of the weather forecast. A "hydrostatic" relief valve opens and closes when needed as it attempts to equalize the pool water pressure with the ground water pressure. Human intervention is not involved because the pool is still filled. Hydrostatic valves are great in theory, but seldom work after a few years.
About 17psi at 1.8m