Lots of good information here and some not so good.
You really don't want to sanitize the Black Tank, you want it do a little digesting of paper and solids.
My procedure is similar to many, just a bit different.
We have three waste tanks Black, Galley, and Grey (Shower & Vanity). I also have a clear 45 degree elbow, to observer the drain process.
First I drain the black tank, once most is drained I then turn on the flusher (Connected with my general use garden hose). Then after a bit I set the timer on my Smart phone for 3 minutes, and Close the black tank valve (CAUTION DO NOT GET DISTRACTED!!!) When time is finished I open the Black tank Valve and let the rest drain out. Then turn off the flusher, and close the black tank valve.
Next, I drain the Galley tank, semi clean water maybe a little greasy and small food particles.
Last I drain the Grey tank, shower water, clean slightly soapy water, this will rinse out the stinky slinky, leaving it clean when disconnecting.
I keep the slinky and all fittings in a Vinyl 5" X 8'fence post under the 5er.
