I have an extra brass check valve laying around and I just put in a sand point well. I thought maybe I could fashion a vacuum breaker by drilling and tapping both sides to accept an air valve. The hardware store has those little schrader style valves that you see on your car tires but with 1/4" npt male thread. With one of these one either side of the check valve I think this would allow air in should the water try back flowing, thus breaking the vacuum. This would be on the discharge side of the shallow well jet pump. Under normal circumstances the pipe between the check valve and the pump should be at system pressure, and the pipe after the check valve would lose pressure whenever the systemshut down. This is a lawn sprinkler system. Am I missing something? Any reason this would not work?