That quick clog makes me suspect that too much Tp is being used. You cannot use as much TP per job as you did in the S&B house. I'm solo, so cannot advise with your 3 adult situation. Make sure they are flushing only TP and not facial tissue, baby wipes, paper towels, cotton balls or anything else that won't readily disintegrate in the water. I use TP from Costco (Kirkland brand) and in 3+ years of full-timing, I've never had an issue. I dump the tanks when they're full unless I'm hitting the road.
BTW, I do use chemicals, purchased at Walmart. I've never used that $1 a sheet thin stuff CW sells.