Practical Sailor did not like the Raritan
valve saying that "it didn’t resist stale urine as well as other valves. It became stiff, lost
resilience, and leaked (in the lab and on the test boat)." That was about all they said about any of the three valves leaking back.
Leaking back is a problem that I would like to solve as well.
I have wondered if a higher column of standing water
might be better than a lower column of water
by putting enough pressure on the joker valve to push it tightly together and sealing it off.
Groco recommended that I not over tighten the bolts that hold the joker valve containing flange together. The thinking being that squeezing too hard on the edge of the valve distorts the duckbill part and keeps the lips from closing properly.