Spa draining when pump is running

[BearOso]

Hello everyone, I am new to the forum.
I have an elevated heated spa that drains into pool (waterfall). When I am running my spa (spa mode), after about 20 minutes the spa water level drops to just above the jets. I have a jandy check valve on the spa return line. When the lever is in spa mode, the check valve flap only opens about 1/4 of the way. Could this be the problem of my spa draining when the pump is running? The picture of the valve is NOT in spa mode.

Thank you

 

[kadavis]

If your valve is in spa mode then you should be getting strong flow out of your spa jets so I can't see how it's draining unless one of the suction valves are out of place or your valve diverter in the pool/spa return is bad.