Jim Richardson wrote:
As a side question. What's your opinion on bladder tanks for holding
tanks?

Bladders are ok for water or diesel, but not a good choice for waste
holding. For one thing, their average lifespan is only about 15
years--not that much longer than metal. For another, it isn’t at all
uncommon for a bladder to blow out its fittings at the first sign of a
clog—even more common in bladders that aren’t vented (which should never
be used for waste holding in any event, because waste produces expanding
gasses that can blow out fittings or even burst the tank, and because
methane is flammable). And because they're designed to hug the
contents, it's almost impossible to maintain 'em aerobically so
controlling odor--not necessarily inside the boat, but out the vent when
the head is flushed--in a flexible tank is all but impossible.

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