Good point.... I was thinking that the entire IBS would essentially gravity drain down into the hard tank. I'm imagining the fill/empty hose from the hard tank entering the IBS right leg via the bottom fitting. When emptying, the water gets sucked out of the hard tank first. It couldn't suck air until that tank was empty, right?
In Bow System
Try it and see what happens. Worst case is you end up ordering a check valve.
Re: In Bow System
X2 they tried to get me to not order a check valve but I had most of the stuff at the house to do it right so I did.
Originally Posted by wolfeman131
In Bow System
The entire system (both ibs and tank) will be full. The suction on the hard tank will cause the water at the highest point to be pulled first. It will pull the water out of the ibs until it sucks it flat. The check valve on the vent from the ibs (check valve #1) will cause the bag to completely flatten. Once the bag collapses, it will be sucking on the tank only. This will draw a vaccum on the tank. This is why the check valve on the tank vent will help you (check valve #2) will break the vacuum and allow air in to the tank so it can drain without collapsing.
You can tee the vent with a check valve on the tank and vent. Just make sure the vent on the tank allows flow in and the thru hull vent allows flow out.
If you don't want to tee it, you can just put a spring check on the vent port from the hard tank. Then vent the ibs through the hull with its own check valve.
Just installed my Integrated bow sack tonight. I installed it just like the diagram I posted, but I did add a check valve to the vent line.
If I like the way that helps the bag empty completely, I may add check valves to both rear vents.
Is there a disadvantage to adding check valves to the vent lines?
Nope it helps drain them flat.