Our WS31 has been giving us fits as well. We too are used to a straight shot into the black tank. Ours has a curve/bend in the pipe maybe 6" below the opening. We have had it "burp" when flushing and spit guk out of the bowl! EEUUUWWWW!! My DW has had to resort to clearing the obstruction with a coat hanger. She is a smart cookie tho. She left the wire ends where they are originally and used it like a loop so as not to damage anything...
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