There are two areas where you will find water check valves. The first is in the plumbing from the pump, just after the pump-to-tank recirculation valve and just before the foam concentrate injection port just ahead of the foam manifold. This check valve prevents foam concentrate from backing into the pump-to-tank recirculation valve resulting in foam build up in the water tank, and it prevents any chance of foam concentrate backing up to the pump. The 2nd location to find check valves in the water system is at each CAF capable discharge valve. The water line discharge check valves prevent compressed air from entering the water system.
Similarly, at each air discharge valve, there are check valves that prevent water from entering the compressed air system.
If compressed air could back up into the water system far enough (through 2 check valves) cavitation could occur. However, if water could back up into the air system and reach the Air/Oil Separator (AOS), the water could be mixed with and dilute the oil and slowly fill up the sump (Refer to the Site Gauge). Neither issue is field corrected, and requires notification of the F-7 certified EVT Mechanic.
