Things You'll Need
Hydrostatic relief valve
A hydrostatic relief valve is typically installed in the deepest end of an in-ground swimming pool to relieve ground water pressure when the pool is emptied. A typical residential pool holds 20,000 gallons of water and provides over 150,000 pounds of force. However, when a pool is drained and there is ground water present underneath, the pressure of the ground water could cause the pool to "float" and become damaged. A hydrostatic valve relieves this pressure.
Drain the swimming pool by opening the main drain valve. This could take several hours or days.
Locate the main drain, disassemble the drain grating and remove the dress ring. Use the screwdriver to remove the grating.
Install the hydrostatic valve onto the valve stem. The valve typically has a male threaded end that fits into the valve stem opening. This can be hand tightened.
Replace the dress ring and drain grating. Secure in place and refill the swimming pool.