I had the same problem, two years ago, in New Caledonia, with the fore cabin heads.
Since I was receiving friends the next day, I was rather worried and was looking for a speclialist in cleaning tank.
Before he came, I had another idea: I openned the vent on deck and poke with a broomstick. it appeared that the discharge valve is just underneath the vent, and vertical. In 2 minutes the job was done, unfortunately in the Marina du sud in Nouméa.
Simple things sometimes work
----- Message reçu -----
De : svbebe
À : amelyachtowners
Date : 2009-06-03, 23:34:37
Sujet : [Amel] Re:Head discharge hose clogged with calcification and vinegar as a solution
[Non-text portions of this message have been removed]