Originally Posted by Sailmonkey
99.9% of manual marine
heads have a hose from the pump to the backside of the bowl to supply flush water
. I'll admit that I don't have a lot of experience with electric
heads, but would bet they're similar. Heads that were intended to be freshwater flush may not have this hose.
Not all manual toilets have a hose connecting the pump to the bowl either...the Groco and Wilcox-Crittenden "bronze thrones" and the Baby Blake that all have a foot pedal control for flush water
do not...leaving no place to put a vented loop BUT the intake line.
All the basic electric
toilets--Jabsco 37xxx series and the Raritan
Crown and SeaEra--do have a hose that connects the pump to the back of the bowl, but the high end all china
models do not. However, most have internal vented loops, so no need for another. The solution for most that do need one and have no place but the intake line to put it is an electric solenoid valve installed in the loop instead of the regular air valve that's wired to the flush button. Flushing
the toilet closes the valve to allow the toilet to prime...releasing it opens the valve to let air into the line to break the siphon started by flushing
makes one...part # is 37068-0000
Btw, vented loops should be installed at least 6-8" above waterline *at any angle of heel*...which on most sailboats requires it to be about 3 FEET above the bowl. This will require replacing the short piece of hose the toilet mfr uses to connect the pump to the bowl with hoses long enough to put the loop where it needs to be.