Help me understand this basic Pool & Spa Combination plumbing diagram?
My understanding, which is very limited, is that this setup would be for a Spa that's physically higher or at least fills higher than the pool. The actuator valve would only keep both bodies at a level height &amp; equally heated.

But, with the actuator valve's Spa return closed, only then can the Spa overfill &amp; even up to an overspill. Also, this setup would then allow for the Spa to be overheated or heated above the pool's temperature.