BF wrote:
I've never seen a joker valve (lots of duck bills though).

Hmmmm....we may be talking about the same part, but Jabsco,
Wilcox-Crittenden, Groco and Jabsco all call it a joker valve in their
exploded parts views. The only mfr who calls 'em duckbills is SeaLand.


From my
visualization of your description what is probably happening when you
over-tighten the screws is not puckering of the sealing surface...

Yes, it is a puckering of single piece of rubber (the flange on the
joker valve) between the flange on the on discharge fitting and the pump
body. If over-tightened screws are backed out a bit within a short
period of time, the rubber regains its shape and seals the leak...but if
the screws remain too tight long enough, they deform the rubber
permanently...the only fix is a new joker valve.

but
deformation of the flanges between the screw points causing a reduction in
pressure between the two flange surfaces.

Huh????

O-rings seals, when properly designed and manufactured should be assembled
with their flanges in contact with each other, ie bottomed out. Obviously
referring to face seals here and not radial o-ring seals.

I think you just WAY over-complicated something that's really very
simple... All we're talking about here is two pieces of hardware
(usually hard PVC, but can be bronze on older toilets) with a flat piece
of rubber between 'em, held together by 2 or 4 screws.

You can see the parts in question in the exploded drawing of the Groco
Headmate he
http://www.groco.net/images/toilets/...-SM/HF-pg2.jpg (click
on the drawing to enlarge it to a readable size)... parts #14 (discharge
fitting connector) and 4 (pump body) with part #16 (joker valve) between
'em). It's the same on all toilets, and you can see by also going to
the drawing for the Raritan PH II he
http://www.raritaneng.com/pdf_files/...Ephiiv0303.pdf

--
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