Hmm, I like this idea. Running that airline down into the bottom of
the tank with lots of holes would also let you aerate stuff if you
were in a no discharge zone. A 12 V air pump is 1/10 the cost.

What kind of tank do you have? I would have to pump against the head
pressure of the tank being below the waterline so would need 2 - 3 psi
which is a fair amount for a plastic tank. I would sure hate to bust
something.

--

Roger Long



"Terry K" wrote in message
oups.com...
My waste tank is purged to the sea or, with an external hose
connected,
to the Wall Mart plaza storm sewer like RVers do it, or an external
tank, like my porta pottie from the truck, using air pressure. We
don't need no steenkin' macerator pump, nor no 'nuther pump neither,
except the 12vdc tire pump, which pressurizes the system enough (1
or 2
lbs overpressure) to blow the "ballast" out the marine discharge. I
use
a plastic ball valve as a sea cock, and it doesn't leak. Nor does
the
joker valve, even with pressure on.

The only time I open the cheap plastic ball valve / sea cock / port
/
sea valve is when emptying the holding tank. The only valve, aside
from air vent valves in the system, is the one sea cock ball valve.
There is a tee between the head, through hull / sea cock, and
holding
tank pipe.

Two minutes of pumping air into the tank with the air vents closed
and
the sea cock open and it all goes out. Then, it farts to let me know
it's done.

Terry K