[Komal]

I want to do helium leak test for big valve and valve need to pressureize with helium at 2000 to 3000 psi pressure, Vloume of valve is 30 liter of water, if i feel valve with 25 liter of water and than pressurize the cavity with helium what reaction will happen, helium being non soluable to water will have same pressure on all the walls of valve.

[Enthalpy]

You will get a uniform pressure, yes. But is this all you want?

Usually, helium replaces the working gas or liquid during a leak test because helium leaks much more than other fluids. If you keep some water in the tested volume, will you test all the parts you want?