tinmanny, I have a buddy with a 190gal and he his wc almost completely automated. Has a 40 gal plastic resivor above his sump. The amount of water that is in the second chamber of the sump is 20 gal. He always has 20 gals of rodi via float valve in his plastic resivor. When it's time to change the water he simply adds the salt in the top opening of the resivor, lets it mix overnight via pump and heater in the resivor and then in the morning, he shuts his sump off, opens a drain valve and drains the sump dry. While the sump is drained, he simply sponges out the sump chanber, then he open the valve from the resivor above the sump and the water fills the sump chanber. Entire process taks 5 minutes, including adding the salt the night before, turning the sump off, draining sump chamber, cleaning w/ a dry sponge, and filling. My next build will be modeled exactly after this concept, except I don't have a drain near by so I'll have to pump from the sump chamber to the shower.