Hi Peggie et al
This is Howler (aka Dan) the original poster of this thread. I read your
advice and did the recommended troubleshooting. I even bought your book and went through its troubleshooting section.
Here’s the situation.
1. The
holding tank is near empty.
2. The vent line is not clogged and has no sags (the
boat is a brand new 2018 Beneteau)
3. The issue seems to occur after sailing in big seas. For example today we were sailing in 5 foot waves coming from abeam, and heeling quite a bit in 20+
knot winds, after which the problem recurred.
4. The air vent is connected to the top of the
holding tank as it should be.
After that, when emptying the
head, the waste comes out of the air vent thru-hull. And it’s more than just an amount that could accumulate in the air vent hose from seawater entering.
The only thing that solves the problem is to empty the (tiny quantity) of waste actually in the holding tank through the gravity discharge valve. After that it operates normally again.
This leads me to think that there’s some kind of air pressure build up from the waves or heeling, which is relieved when the holding tank is emptied. But it’s still an enigma how the
head can empty directly to the air vent just because of some air pressure. Again, the holding tank was near empty both times this occurred.
Any addition additional ideas? Thank you.