I think most will have their own formula...here is mine.
I have a 50 gal black and 65 gal gray. With each when I get ready to travel, i will dump both, rinse the black and then put about 5 gallons of clean water into each tank. I will then put one cup of liquid laundry detergent (I use Oxy-Clean) and one capful of liquid Calgon into each tank.
Arriving at destination, I will drain both tanks and again put about 5 gallons of clean water back into them. While at destination, we will use both tanks normally and trump if necessary. When we get ready to travel to next destination, I will repeat the process.
Ron
Ron & Sandie
2013 Tiffin Phaeton 42LH Cummins ISL 400hp
Toad: 2011 GMC Terrain SLT2
Tow Bar: Sterling AT
Toad Brakes: Unified by U.S. Gear
TPMS: Pressure Pro
Member of: GS, FMCA, Allegro
RETIRED!! How sweet it is....