"Peggie Hall" wrote

???? I can't see how that would work in any marine sanitation
system.

Back when I was a young pup in a design office drawing piping
schematics for passenger vessels I used to put these in on every
sanitary piping plan because they were on the plans they gave me as a
"go-by". These were large vessels by yacht standards, generally with
ordinary jet flush toilets like you would find in an office building.

I can't see any reason why it wouldn't work in a fresh water flushing
system. Even if you had a large flushing tank, you might want to be
able to replenish it from the main tank; especially if you were
running an RO system into it.

Here's how it would look:

http://home.maine.rr.com/rlma/Flush.jpg

On the large vessels with engineers monitoring everything, the float
switch was just a manual valve and the flush tank large enough for
about a day's use.

My sink drain connection to the head intake is just a variation of
this. If I simply added a 2 -3 gallon tank into the line, which I
have some minimally useful space to do, I could easily set the system
up for several unattended FW flushes. This is something I might want
to do if I planned to visit some place like St. Johns, Newfoundland
where the water coming into the head might well be dirtier than the
water flushing out of it

--

Roger Long