The standard, or bleed through, versions allow a small amount of leakage between port 3 (pilot) and port 2 (inlet), which aids in purging air that can be trapped in the pilot circuit. Versions with sealed pilots may be sluggish to close because of trapped air.

All four-port vented valves have a sealed pilot. On 4-port vented valves, port 4 (vent) should never be blocked as seal weepage will eventually cause the valve to malfunction. 1 to 2 drops of oil pass into the vented spring chamber every 4000 cycles; this equates to 1 cubic inch (16 cc) every 1 million cycles.