Here's sump version 3.0!!! Now we're playing with fire...
The two cylinders at the back represent the Herbie drains, and the two cylinders near the front represent reactors. The grey mesh looking stuff represents egg crate to hold a filter pad. There is enough space in the sump so that if the ATO gets stuck on the sump will hold that volume (4 gallons of RO/DI), and then if the power fails at the same time and the overflow chamber of the tank drains (it shouldn't anyway) it will hold that volume (9 gallons) as well with about 1 1/2 gallons to spare.
The overflow chamber holds 9 gallons, and I will design the plumbing so I can pull the Herbie emergency standpipe, the overflow will drain to the sump, and I can use the return pump (with a tee to a hose to a bucket) to pump that 9 gallons out for easy water changes. A little smaller than I'd like, but maybe I can figure something out to get a few more gallons down to the sump. The skimmer area is 15 x 12" and would probably hold something even bigger if it fits in there at an angle.
