I'm at a loss. I'm pretty sure it's a check valve issue with my spa but for the life of me I can't locate where the valve is located. I have separate equipment for my pool and spa and looking at the layout of the spa equipment it doesn't look like there is a check valve at all. What seems to be happening is the spa will drain to the level of the pool and reading all the threads has convinced me it's a check valve. Can someone take a look at the layout and tell me I'm not crazy.
Picture one is the spa equipment layout
Picture two is the pool equipment layout