The further away the valve is from the sump the harder it will be to tune, it can be done but it takes longer for it to "settle" after each adjustment. The issue relates to the pressure difference over the valve and the further away the valve is from the sump the higher the vacuum effect after the valve which is ultimately what causes the noise (almost like cavitation). Adding an additional valve at the sump level is a decent solution, even if it's just a ball valve, it will allow you to reduce the pressure difference on the first valve and hence reduce the noise there while also making it easier to tune.
|