BoatBanter.com - holding tank plumbing

John Knox wrote:
I am planning to replace the connections for my
built-in holding tank. They are currently 2
1.5" nylon hose fittings on the front face of
the tank - one at the top as an inlet, one at
the bottom as an outlet. Is it acceptable to
use just 1 top mounted fitting, with a tube
running to the bottom of the tank, for both
in/out?

No...you'd just be asking for trouble. If it ever became clogged, you
wouldn't be able to use the toilet OR empty the tank. How would you
flush water into the tank through the toilet during pumpout? What if the
valve should accidentally be left in the pumpout position when someone
uses the toilet?

It would require a valve or 2, but it
seems to me that it would help keep things
stirred up, and make 1 less hole in the tank.

There's no reason why you can't run a pipe from the tank inlet fitting
to somewhere near the bottom of the tank, or put both inlet and
discharge fittings on the top of the tank...just keep the inlet and
discharge fittings separate.

I can appreciate wanting to keep the number of thru-hulls in the boat to
a minimum, but see no benefit whatever to reducing the number of holes
in a tank--especially at a cost of increasing the number of valves to
maintain (or break if you don't). In fact, when the tank is to be dumped
at sea as well as pumped out, the ideal solution is TWO discharge
fittings in the tank, which eliminates the need to put a y-valve in the
pumpout line.

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