I have a pool with an above ground spa. As with most pool plumbing, I have two actuator valves for spa vs pool drain, and spa vs pool return. They are working in sync to be either spa drain and return, or pool drain and return. This makes sense when heating up the SPA, but do they alway work this way. I was under the assumption that the controller would once in the while drain the SPA in the pool and get fresh water from the pool, but it does not seem to be the case. Are all pool plumbing working this way, which means that you have to maintain the chemical balance on individually in the SAP and the pool?