Noeta wrote:
Changed a few things (raised the vent a bit) and it still does not work.

The bowl is roughly at the water line, and the loop/ vent is 25" above that.
Still floods.

I've tried removing the valve entirely and creating a hole in the loop after
flushing and it still siphons.

Damn! That means it HAS to be a siphon...something has to pulling it to
create the siphon, 'cuz there's no way that water can flow over a loop
25" above waterline passively...water doesn't run uphill! But even so,
why isn't the air break in the vented loop breaking it?

I'm gonna forward this whole thread to a couple of my gurus...'cuz I'm
stumped!

Also tried it with the through hull outlet
closed to make sure it wasn't coming in that way.

I wondered if the intake was actually the source. Is your tank filling
up when the intake seacock is closed?

The waste line had a pre- existing loop in the same area. Now I'm thinking
if the water loop doesn't work the waste vent won't work either.

Let's not worry about that one till we solve this problem.


--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/books...ku=90&cat=1304