I've never seen a joker valve (lots of duck bills though). From my
visualization of your description what is probably happening when you
over-tighten the screws is not puckering of the sealing surface but
deformation of the flanges between the screw points causing a reduction in
pressure between the two flange surfaces.
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.
BF


"Peggie Hall" wrote in message
om...
Skip Gundlach wrote:
I *think* I know the joker valve to be the duckbill at the outlet.

Yup...the little rubber cup shaped thingy with a slit in the bottom and
"lips" on the outside that's in the discharge fitting. The flange
doubles as the gasket between the discharge fitting and the pump body.

If you overtighten the 4 screws that hold the discharge fitting onto the
pump body that connection will leak onto the head sole.

This applies to electric macerating toilets as well as to manual toilets.

--
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