Walmart Toilet Chemical vs. RV Dealer Toilet Chemical

How much water do you use. When I flush I use lots of water and I never have any odor. Also, I do not use any chemical additives. Lots of water is the secret. I would check under the bath room sink. Se if there is a vacuum break there. If so it may be stuck open. They are easy to replace, just unscrew and screw on a new one. There is nothing wrong with Wal Mart chemicals, many are the same as your RV dealer sells.