Hello,
On the circuit of compressed air, the snorkel has its reserve of air.
A valve with no return makes close the circuit when the principal reserve is empty.
I had a valve from Festo: H-M5 (3671).
The problem is when the pressure in the principal reserve drops slowly; the valve is not closed because the pressure doesn’t move the valve.
The reserve of the Snorkel is emptied and it does not open!
I need a valve with spring to close the system.
I made a valve with a valve of car. It is very easy to make and low cost. The spring is in stainless steel and the body in brass.
Here photograph.
Goodbye
Alexandre