A proportional valve is like a position-seated valve so the seal is never really dependent on torque. So the torque needed to move the valve could be fairly light for a water valve (200-300 in-lbs). I have no guess how the stem is designed to insure there is no air leak in or fluid leak out. I'll be impressed if you're not adding air to the line every time the knob is turned - requiring you to bleed your breaks regularly. Or, you'll have to make your adjustments while the brakes are pressurized but that will make the knob harder to turn. Good luck.