Update - Installed It
Guess I must be the first to install one of these, so here's an update
The Aqua Saver is a device that installs in the fresh water tank, that has an opening big enough to reach in and clean and dry the inside of the tank. It takes a 7.25 inch hole (the company rented me a special hole saw especially for this). The mounting flange attaches with 8 bolts, and there is a threaded cap that seals so it is water tight.
It took about 30 minutes to install, and appears to be a high quality. I won't be able to try it on the road until next season. It was a good feeling, to get inside the tank and wipe down and dry everything for the winter. Next spring I'll be able to sanitize the tank directly, and expect it to take much less time and water to get back in service, and it will be easier to clean the tank from time to time.
Just thought I'd share with everyone. Seems to be a good product and an easy installation, and the company (PJB Industries) handled the order in an outstanding way.