Roger Long wrote:
This business about not connecting FW systems to sanitary plumbing
reminds me of a USPH required and approved arrangment for FW flushing
systems.

What is USPH???

It's called an "Air Gap" and is basically just a funnel with a pipe
outlet a few inches above it. The funnel goes to the tank for fresh
flush water. The valve can either be manual or perhaps controlled by a
float in the flush water tank. If something goes wrong with the
sanitary system, the water just backs up and overflows the funnel with
no way to get into the potable water.

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

--
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://shop.sailboatowners.com/books...ku=90&cat=1304

"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