How to fully drain and clean the black tank

[itat]

I'm using RV Digest-It tank treatment once a year.

Unique Natural Products | RV Digest-It Holding Tank Treatment | Safe Products That Work

[lugoismad]

I use the cheap laundry detergent - I believe its "LA's Awesome" brand from the dollar store. Its a $1 for a container of it. I put half in the black, half in the grey tank, and a few gallons of water in each, after I dump the tanks. This way they slosh around on the drive home and then the next time we take it out, do the same on the way to the campground.

Then when we get to the campground, I add a packet of the chemicals to the black tank.

[Restcure]

We use the Geo Method periodically... nothing else.

[Hack113]

This is our 2nd 5th Wheel & we've used the Geo Method in both. (8 yrs in 1st 5r & 2 yrs in 2nd).
We never had False Probe Readings or Odor Issues from the 1st 5r & no False Probe Readings from the 2nd 5r. We have had Odor Issues with the 2nd 5r, but I blame the Odor Issues on the "Flat-Bottom Holding Tanks" that Forest River has installed in their 5th wheels.
If anyone is not familiar with the "Geo Method", Google it. It is basically using household chemicals in the holding tanks. (Calgon Water Softener, & "Cheap" Liquid Laundry Detergent)
The Laundry Detergent keeps the tank walls clean & the Calgon keeps the tank walls slick.