The best way to reduce and prevent leakage is to constantly test for it or have a detection method in place. Many valve tests are performed with water or air at 3.5 bar, unless looking for a Class V leak.
American Petroleum Institute (API) standard 598 outlines the testing requirements for many types of valves, including ball, check, gate, globe, plug and butterfly. The standard covers acceptable leakage rates for liquid along with gas testing. All valves that have been built to an API standard are required to meet API-598 criteria for leakage prior to delivery from the supplier or manufacturer.
Related recommendation:
CF8 Class 150 ANSI Gate Valve 4 inch
20 Inch ANSI Class 600 Swing Check Valve