Some of our best (and funniest) threads have been about sewage!
Having had a couple of TP pyramids (as opposed to the well-known and dreaded "pyramids of poop"), I have moved to using two types of TP. One is the nice, thick stuff that does not shred, and the other is the junky, thin easily-dissolvable RV TP. The former I put in plastic bags and toss in the trash. The latter, I use for shall we call them "messier" products and I flush those. Actually, both are technically flushable, but it is just safer, in my personal opinion, to not flush the thick stuff.
You need to make sure also that "flushable" wipes are NEVER flushed, nor do you put anything else into the toilet other than body products and toilet paper. No chemicals are really needed, just lots of water, especially if you decide to put all TP in the tanks, as many people do. Tip: Small children need to be closely supervised so they do not use multiple handfuls of TP, and guests need to be told to use less TP and more water. Pyramids of poop are created when you leave the dump valve open at a campsite instead of waiting until tank is at least half to three-quarters full. Liquids dribble out, but solids remain and can harden into a mass which is hard to dissolve and get rid of.
OK, now you have been initiated!