Walmart Toilet Chemical vs. RV Dealer Toilet Chemical

There is no need to use chemicals Walmart or otherwise. There should be no odor inside if everything is working properly. My bet is that something didn't get installed right when it was built. Also I have seen where instead of installing a vent through the roof they put in a short section of pipe with a check valve that is suppose to allow air in but not out. Those are not something I would want as I have seen more than one malfunction.