personally we avoid adding any additional dish soap to the tanks. It foams up to much. However, I do add about a cup of High Efficiency laundry detergent to each tank along with a cup or so of mixed up liquid calgon to each tank. For the black tank I also put in some of the black tank stuff with the microbes in it. Then add a gallon or so of water to each tank as well
Inexpensive and it does seem to keep the tanks clean and the sensors working.
And with the microbe digester, very little odor. In fact, trailers been sitting in the driveway for a week from our last trip, temps in the 90's. and getting ready to flush the tanks, opening the toilet drain and no noticeable odor at all.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!