Vented loop--no discharge line (great lakes)

[Windtherapy]

So I assume since I am on the Great Lakes and can never dump black water overboard and the fact that I don't even have a hose connected to my 1 1/2" thru hull (just plugged the new one), I don't need a vented loop correct?

The vented loop is only for the discharge line when one has that to dump overboard correct?

 

[Peggie Hall HeadMistress]

Technically, yes. But don't be in too big a rush to get rid of the loop...'cuz if your tank is more than about 6' from the toilet and/or the tank inlet fitting is higher than the toilet discharge, a loop--not necessarily vented--can come very handy when installed to let gravity lend a hand in getting the flush to the tank.

This is if we're only talking about a loop in the toilet DISCHARGE line. You do need a vented loop in the toilet INTAKE if the toilet is at or below the waterline, no matter where the flush has to go.

 

[Windtherapy]

I was hoping you would pipe in Peggy. I am coming to realize that just because the manufacturer installed it a certain way doesn't mean its correct. I have diconnected the discharge hose and installed a new thru hull with flange and ball cock and just plugged the valve and wired the valve shut since we can never dump in the Great Lakes. The head itself is almost the same height as the head and the original layout did have the hose from the head to the tank intake sightly higher because it went to the 3 way valve which I have eliminated which I assume worked well since higher. The water intake line did not have a loop higher than the head itself. It ran straight from the thru hull to the head with no loop and the head itself is slightly above the waterline I believe (another O'Day owner could probably verify that). I haven't launched the boat yet so I have no idea how low or high it sits in the water but pictures I have seen of O'Days in the water, it seems like they sit pretty high.