I use 1 cap full, along with the laundry soap, in a gallon+ bucket full of hot water to get about 2 gallons into the black water tank just prior to leaving (the driving agitates it). If it's a long trip I add more water as I go - to get up to 4 or 5 gallons of water in all.
Then after camping I dump the tank (when it is about 3/4 full), add another gallon of water and softner (and soap if I have it), then drive home.
Next trip - add the hot water/softner/soap and go.
Tom and Amy from Northern Virginia.
2000 Allegro 454/Workhorse P32/TST/Crossfire
Life is a DIY project - enjoy it.