Adding water after dumping black tank

I add a couple of gallons to the black tank and sometimes squirt in bit of detergent along with the packet of stuff that's supposed to keep the smell down. The grey tank usually gets some added during clean up once we're home.

One thing to note, is that the black tank indicator may not be accurate. Sometimes ours still shows 2/3 full even after dumping. Sometimes it shows empty after dumping. Also, don't forget that water is the black tank's best friend. Make sure to use plenty or you'll wind up with a pyramid of yuck at the bottom.