Jeff Morris wrote:
This is a common technique, practiced by many cruisers. When I lived aboard, I always
kept a gallon of vinegar in the head so I wouldn't forget.

Peggy has endorsed this in the past (this from last March):

Vinegar ONLY dissolves mineral buildup, it won't do much for dirt and
grime and won't dissolve soap scum, grease or hair.

I did say that...but I've never said that vinegar will dissolve sludge
in holding tanks--which is what he's asking.

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/html/get_ri...oat_odors.html