Peter Bennett wrote:
On most sailboats, the bottom of the head is below the waterline, so
the outside water is likely to flow (or seep) through the pump into
the bowl. If it looks like the water will overflow the bowl while
sailing, it may be necessary to keep the intake seacock closed except
while flushing the head.

Productions boat builders put intake seacocks in locations that can make
that so impractical as to be impossible. My guess (till I hear more from
him) is that a) he doesn't know what the wet/dry lever is for...he's
been leaving it in the wet mode all the time...b) there is no vented
loop in the head intake (which should be between the pump and bowl,
btw...not between the thru-hull and the pump)...and c) he doesn't know
that all thru-hulls should be closed when leaving the boat.
There should be a pump immediately to the right of the head bowl, and
mounted on the same pipe that supports the bowl. This pump has two
parts, and will pump outside water into the bowl for flushing, as well
as pumping waste from the bowl to the holding tank. Do you have a
second pump there?

A Jabsco toilet--which is what he has--has only one dual action pump. In
the "wet" mode, it brings in flush water AND pushes bowl contents
out...in the "dry" mode, it pushes bowl contents out without bringing in
any flush water.

I would think that the only thing that can get into the holding tank
is what you pump there while flushing the head.

Since he's indicated that his bowl is filling with clean water, it's
unlikely that his holding tank is filling to overflowing and running
back toward into the bowl.

Nor is it likely that a fouled joker valve has any bearing on it.
Whizzit that everyone wants to blame the joked valve for ANY toilet
problem, even flush water intake issues???
--
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
http://shop.sailboatowners.com/books...ku=90&cat=1304