Inlet Anti-siphon Loops Suck

[Kim Efishoff]

Peggy,After buying a Raritan toilet (the Cricket), I noted that Raritan suggests installing an anti-siphon loop on both the inlet and discharge sides of the system. This makes sense, as one would not want siphoning to occur through the toilet on either side. Question:Because a standard anti-siphon duck-bill valve allows air to be drawn into a system, what prevents the inlet side of a vented loop system from sucking air instead of water when the toilet is pumped? The dilemma is, of course: one does not want to siphon the sea into one’s boat through the toilet, but one does not want to suck air through the inlet when recharging the toilet with clean seawater. Raritan must have had something in mind when they designed these systems. What’s the solution?Thanks for your help.Kim Efishoff

 

[Peggie Hall/HeadMistress]

The solution is the location of the vented loop

You're right that a vented loop between the thru-hull and the pump would pull air into the line, preventing the pump from priming. But that's not where it goes.The vented loop has to go in the line between the pump and the bowl, 'cuz while the pump pulls water in from the thru-hull, it pushes it into the bowl...and vented loop doesn't interfere with anything being pushed through it. And btw, a vented loop should be at least 8-12" above the waterline at any angle of heel...which obviously means that the short piece of hose connecting the pump to the inlet fitting on the back of the bowl has to be replaced with enough hose to put it that high.