For the past 7 yrs.we lived in our 5vr traveling constantly.
Full tanks, empty tanks.........lots of stuff has been in our tanks.
'Nar a chemical used. No smells, no odors.....because ALL the barriers that prevent odors from coming back inside rig worked. Gaskets, seals, vents are designed to keep odors out.
And when dumping I didn't have odors either because the sewer hoses and connections had seals that stopped waste water from leaking out when flowing and odors from getting out when no flow.
Dumping tanks with high levels.....weight/volume of liquids helps to carry solids out.
Flushing tanks after dumping......helps rinse out solids left behind
Adding water after dumping.....helps keep stuff from sticking and drying out
Water is an amazing tool.....no help from chemicals needed.