Wait a sec...

A vented loop can be made from half of a 2 part "P" trap intended for use
under your kitchen sink. The proper style has a drain plug on it's normal
bottom.

The plug may be fitted with a shraeder valve, like on your bicycle inner
tube or car wheel if you care to roll your own. The shraeder valve must
be adjusted for a very low pressure seal by adjusting it with a shraeder
valve tool. You should be able to blow through it, but not suck.

If I'm understanding what you're saying, it should be just the
opposite...'cuz the function of a vented loop is twofold...1) it creats
an arch in the line above the waterline...and 2) it's suppose only alow
INTO a line, nothing out.

The vented loop is created by mounting the trap upside down on the top of
two vertical pipes connected to the remainder of the piping in use. If
vibration tolerant couplings are used, rigid pipe may couple to other
piping, or semi flexible plastic pipe. I would use an MJ, or mechanical
joint Have used several with excellent results. The MJ was invented for
the Diefenbunker, nuclear defence against toilets backing up with over
pressure shock waves. The p trap should be situated at a point that does
not usually go below the waterline, but that is negotiable. It's function
is to allow low atmospheric pressure inside the piping to "suck in" air,
thus defeating any syphon effect which would otherwise occur.

Wouldn't it be a lot simpler and cheaper to simply drill a hole in the
trap and buy an air valve to put in the hole?

Proper anti syphon loops are available in cast platinum at marine stores.
Lesser metals like bronze are almost as expensive.

PVC vented loops are also availalble, and priced pretty reasonably.


You should be able to see if the head is pumping water into it's self when
you pump the pump. If it is, flip the little lever switch you will find
if you look, and pumping again, observe the head is pumped dry and your
tank will not fill so quickly.

Simply put, the most water efficient way: ahead of use, pump the head a
couple of times to wet the bowl...switch to dry. After use, pump enough
times in the dry mode to move the bowl contents all the way to the tank
(or out the thru-hull if at sea beyond the "3 mile limit")...switch to
"wet" for only enough pumps to rinse the bowl...then back to "dry" to
pump the "rinse water" all the way through the system.

Before you ask...any marine toilet that's working anywhere near spec can
move bowl contents at least 6' in the dry mode. If your tank or
thru-hull is significantly further away than 6', it's a badly designed
system.

you will need to replace, or possibly only clean the duck billed,
or joker valve.

As a live-aboard, replace it once a year...the average "weekend warrior"
should replace it at least every two years.

Buy one, since you will need a spare, then disassemble
the pump to replace it.


Why should you need to do that? The joker valve is in the head discharge
fitting, which isn't part of the pump, but only attached to it.
Replacing a joker valve only requires removing the screws that hold the
discharge fitting onto the pump.

If the old one is torn or warped you will need to
replace it, if not, you may be able to clean it.

If it's more than a year or two old, the slit will no longer be a slit,
but a hole...no longer able to function as the one-way valve it's
designed to be. Regardless of any other condition, if you can see ANY
daylight when you look through it, replace it.

I've never seen one torn that shouldn't have been replaced at least a
decade earlier.


Three lobed valves mimic heart valves, but without ligaments, are not as
reliable as possible.

Joker valves don't have lobes...the most common are a cup with a single
slit...a few are a cup with a + in the bottom instead of a slit...but
they're all just cup shaped doodads with a flange (that doubles as the
gasket between the fitting and the pump), a single - or + slits in the
bottom, and "lips" on the outside of the cup.

Crap overboard when you can. A flexible snow slider carpet may be of
assistance keeping topsides clear for neccessary bodily functions. It can
be towed by floating line to rinse, and seized up using the commissionaire
knot, a crochet, over the bulwark to be used.

Wouldn't a bucket on a long line be a lot cleaner and easier?

As for the rest...you have a wonderful imagination, Terry..but not a lot
of practical experience. If I'm wrong about that last part, please send
demonstration videos shot in 4-6' seas at least 20 miles
offshore...I'll add narration, send 'em to "America's Funniest..." and
split the take with you.

--
Peggie
----------
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