SMC Networks KKA Series Operation Manual page 10

(9) Water is an incompressible fluid. The piping design needs to take the fluid characteristics into
consideration.
If there is piping with a plug and socket with a check valve that is filled with water, and another
valve which is closed while the plug and socket are separated, the pipe from the check valve to
the closed valve will also be filled with water. (See the circuit below)
Once the plug and socket are separated in above condition, they cannot be re-connected
because the water needs to be compressed.
Check valve on both sides：
Check valve on one side:
Circuit Example
Plug and socket connected
Circulating
Valve
Fluid Supply
Valve
9
Drainage