I had this thought the other day and figured I would ask here first. Right now all my sacks (except one) are on aerator pumps. The one not on aerator pumps sits in the bow. Essentially every time I ride I pull one of the caps to burp the sacks. I have a fill and drain line but no overflows since the sack will generally push out through the drain line when full. However there is still air in the sack at the top due to simple physics.
My question is....Can I buy a one way valve that lets out air but not water? That would be a super awesome setup allowing me to fill all of my sacks without plumbing and overflow line to simply purge the air out. If not I may just buy some spring actuated valves that I can press to purge the air out of without plumbing a separate line to the drain line to purge.