Vented Loop

[MaryEllaRose]

I‘m in the process of replacing the sanitation hoses on my ‘90 Catalina 25 and have discovered that there was no vented loop on the toilet discharge line. These the original hoses. There is a slight uphill run from the toilet to the entry point on the top of the holding tank but the tank and the toilet are pretty much on the same level. Should I include when I replace the hoses? There’s not much room to add one and keep it significantly higher than the top of the tank.

 

[dlochner]

No need for a vented loop, although a high loop would be helpful in preventing back flow from the tank if the boat is heeling. High means high enough that the contents in the hose will drain back into the tank.

Vented loops are necessary for overboard discharge to prevent siphoning and they go after the pump. When pumping water through the loop event closes due to the pressure. When pressure is relieved due to the pump stopping, the van opens and breaks the vacuum preventing a siphon from forming and flooding the boat.

 

[Peggie Hall HeadMistress]

No need for a vented loop, although a high loop would be helpful in preventing back flow from the tank if the boat is heeling. High means high enough that the contents in the hose will drain back into the tank.

It only needs to be a few inches higher than the top of the tank and has the added advantage of makiing it necessary to pump long enough to push bowl contents over the top of the loop...gravity will get it the rest of the way to the tank.

A vented loop in the toilet intake IS necessary. It does not go in the intake line between the thru-hull and pump, it goes between the pump and the bowl and needs to be at least 6-8" above the boat's waterline at ANY angle of heel, not just when the boat's at rest. That puts it 2-3
FEET above the bowl on most sailboats. This will require replacing the short piece of hose the toilet mfr used to connect them with two sections of hose long enough to do this.
--Peggie

 

[MaryEllaRose]

We flush the toilet with fresh water from a dedicated tank. Do I still need the vented loop between the pump and the toilet?