Forget the check valves, they are not there. Â They are air venturri lines that supply air intake to the WATER jets. Â That is what gives you the air water mix. Â The motion of moving water pulls air into the jet stream by venturri action.
Sit against the jet and block the water from coming out, well guess where it goes. Â Cover your mouth with water coming out and the water comes out your nose. Â Nothing is wrong here. Â Run the jets and open the air venturri's to clear them of any water. Â It is a natural action.
If you block the water from coming out of the jets, or the ozone inlet, it only puts back pressure on the water to seek an altenative route. Â It is possible to start a venturri syphon draining action that will drain the spa until the water level drops to the level of the air intake, then it will stop. Â Again, no problem here either.
Cancell the service call, it is not covered under warranty.