I've had this disgusting problem a few times and attributed it to someone over-flushing the head, but I think there's a problem with the head:
After a few days post-pump-out the head has back filled with blackwater while sailing and once while at anchor. First few times this happened I chalked it up to a guest over-flushing, got it pumped and went on my way. The Jabsco head is 3 years old. The system was completely redone by previous owner. It was a very well done job, no mickey mouse stuff on the surface, all new hoses and recommissioned blackwater tank. I checked the Jabsco manual and all appears to be piped correctly. The last trip was the last straw. I had to go below every 10 minutes and scoop some very disgusting water out of the bowl and pour down sink drain otherwise it would have overflowed. After a couple of hours of this the shine wears off, believe me. So - my plan is to take out the pump/valve assembly and look for a failed seal. Should the head discharge hose-to-tank have a check valve in it? I think not because it would become fouled with solids. I'm aware of principles of siphoning but short of drawing a diagram I don't think siphoning is the problem. I can't think of anything besides a failed seal. Help! Steve Hood S/V Diamond Girl C&C 34 Lions Head ON _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com