I now have two new questions. Both illustrations of the joker valve
show it aligned in a vertical position. Is this necessary?

When all else fails, follow the directions. A vertical alignment
does a better job of preventing leakage than horizontal...and in some
toilets, the fitting isn't exactly round. The joker valve only fits
correctly if aligned as shown in the drawing.

I just
took my head apart and there was an 1/8" gap between the lips so it
leaked sewage back into the head.

That's a good sized gap...and illustrates why joker valves should be
replaced at LEAST every two years...every year if you live aboard.
However a joker valve isn't supposed to prevent slow seepage, only a
flood. I suspect you aren't flushing long enough in the "dry" mode (if
you ever flush in the dry mode at all) to move the waste over the top of
the vented loop. Even if you have an electric toilet that doesn't have a
"dry" mode, the only thing that should run or seep back into the bowl is
clean flush water...if waste is running back, you aren't flushing long
enough.

I don't remember what the
orentation of the slit was.

Check the drawing for your toilet. If you don't have a drawing, you can
prob'ly pull one off the mfr's website...what's the make/model?

Second. I saw a three "lip" joker valve at West marine. Is that a
better arangement than the two lip valves shown in the diagrams?

The jury is out on that one. The X or + pattern was supposed to be an
improvement over the slit...but I know of a couple of mfrs who tried it,
then went back to the slit.

Have a happy Thanksgiving, y'all!
--
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