If you have the space, or if the top of the head is below the static waterline, you really should have a vented loop. Its purpose is to prevent the plumbing from syphoning back into the boat.
Even if a boat's head is high enough to be above the waterline at rest, it will not be so when the head is on the leeward side in a breeze.
The joker valve that Waterline refers to will act as a check valve, but debris lodged in them will prevent a proper seal and they do weep more as they age. Even a small leak could sink your boat if you are not there to see the problem.
Another thing if you have a vented loop - remember there's more hose to clear so more pumping is required during a flush.
12-01-2006 09:48 PM
You can get a lot of water through a 1.5" hose.
12-01-2006 04:45 PM
If you go by the book you should have one but even the vented loop can clog. If the head is above the water line there should not be a problem. I don't think its necessary anyway since the head has an anti back up valve which should solve the issue. Lots of things would have to fail for a problem. I don't have one on my Raritan head on my S2 11.0A and have never had a problem.
12-01-2006 04:28 PM
I'm installing a Wilcox-Headmate in my Catalina 30 this weekend to replace the same model head. It does not have a vented loop...should I install one, I would rather not?