Raised Spa slowly loses water (check valve placement??)

[Torch]

We have a built in pool with a raised spa.  It is plumbed with pretty much the standard single pump pluming for a pool and hot tub. It has automatic Jandy diverter valves.  The builder did not install check valves to address the raises spa in the case of water seeping by the diverter valves.  At first it was minimal but as the diverters ages and the seal more it became more pronounced.  I have replaced the diverters a few time now and, while it helps, it does not completely cure the problem by plumbing in check valves.  

I think I have it figured out but, before doing all of this I want to make sure that where I plan to put the check valves is indeed the correct placement.  I have not dug everything up yet nor can I really get good pictures (tight area stuff in the way).  I did a simple drawing on SketchUp with just the basic valving related to the pool, spa, pump and filter and where it seems to me that I need to put the check valves.

If someone that is experienced could confirm that what I am thinking is correct or, if it is not, why and what is correct I would appreciate it.

I think the drawing is fairly clear but if not, please ask.  The red arrows show where I think the check valves need to go and the direction of normal water flow. The diverters in the drawing are in pool mode in the drawing.

Thanks

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[Torch]

I should have mentioned, there is not "spa makeup" plumbing.  When the spa is on, no water goes over the spillway.

[Fletcher Pearson]

Honestly, your issue is super common and a lot of builders skip check valves for some reason. Adding them should solve the problem for good. Just make sure you get good quality check valves (swing or spring-loaded, depending on your flow needs). Silverline pools

Sounds like you’ve thought it through, so go for it!