The little compartment is a RO/DI reservoir...when the chamber all the way on the right evaporates, the Tunze Osmolator kicks in and draws top off from the reservoir as needed. That reservoir has a float that will automatically fill up and shut off as needed.
The compartment next to the RO/DI and below it is the new Saltwater mixing area. When I do a water change, I will pump it out and into the main sump area. NEVER GETTING WET!!!or lifting a bucket. A mag 7 will pump it into the main sump.
You can see the aquarium return and the skimmer return dropping into the main sump. it goes down and back up and flows over the far right chamber where at the bottom has a 1100gpm pump the returns the water to the tank via the chiller. which I can bypass if i need to for servicing.
Simple!!! and NEVER get wet or lift a bucket. I also just turn a valve, and pump the waste water into the sewer system!!!!!! no siphoning !!
Todd