Video will show how to go about troubleshooting vacuum water flow alarms.
There is a strainer inside the on/off valve see picture below.
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Inlet Strainer inside on/off solenoid valve. Many times this will plug up with sediment. It can be pulled out and flushed out. Slotted screw is the manual override also.
Possible Alarm Codes for this video are:
700033 - Warning - Vacuum Pump Supply Water Flow Too Low | Titan 3000 Series
700048 - Vacuum Pump Water Flow Alarm | Titan 2000 and 1000 Series