What does four-way valve mean in practice?
The hydraulic ASO valve compares feed and permeate pressure, shutting off flow to the membrane once the tank is full.
When does it matter?
A leaky control membrane or incorrect port connection causes continuous sewage flow even though the tap is closed.
Which solutions are related to it?
The IN-OUT directions, supply and tank pressure, and the ability of the valve to close after a few minutes are checked.