Raised spa with only 2 main returns (spa and pool return labeled in red). I've included a pic of my setup for reference. I have an in-line backflow preventer on the spa return (light teal circle) which I think is bad and not working correctly. I don't even see the flap inside opening or closing when I turn the jandy valve and open flow to the spa return. Yesterday I decided to close off the return flow to the spa completely (normally I keep it open a little) to test and see if it would still loose water with that jandy valve (yellow circle) closed off to the the spa return. I figured if it stopped losing water, then it was definitely a faulty backflow preventer. At first it look like it was working and not losing any water, so I decided to let the pump run and wait overnight to see if the water level dropped in the spa...but when I came home today, the water in the spa had dropped about 5-6". Do you think it could also be a bad jandy valve not sealing off properly? If the jandy valve would seal off properly, wouldn't it not make a difference if the backflow preventer (light teal circle) was faulty because it would still be stopping backflow at the valve itself right? I may be wrong, I'm by no means an expert on any of this...so please let me know your opinions! TIA