Control Valve Question: Flow Up vs. Flow Down

Suggested definitions:

1. Flow up goes through the port first and past the plug second.
2. Flow down goes past the plug first and through the port second.

As pressure drop increases, 1 will cause the valve to close more easily and 2 will make it more difficult.

There may be cavitation issues to consider, and the manufacturer's recommendations on installation direction should be followed for best results.