Haven't you written elsewhere that the olive oil will prevent the necessary
air from getting to the contents of the holding tank?

It depends on how much oil. A tablespoon once every couple of weeks
prob'ly won't cause any problems...but one or more "glugs" of it down
the toilet at once will put an "oil slick" on the surface of the tank
contents that will seal it, turning the contents below anaerobic...and
therefore VERY ripe.

--
Peggie
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Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1