05 LSV losing water from middle ballast

I have a Gravity I. I notice that the center ballast loses water over time, probably about half a bag in an hour. I would normally just say it has a leak, but a) I do see what coming out of the exit port sometimes when the boat takes off and b) it seems to only lose water when we are moving; if I fill it up, then we park for a while, I don't notice that the water is lower.

Has anyone had a problem with the ballast siphoning out or something like that? Or should I just take it out and look for a leak?

Same thing on my 05 w/gravity III. Added a 3/4" pvc ball valve in the drain line. Fill the bag, close the valve and it stays full.

I just made sure teh conections are tight. If you have never removed the bag, take it off, check the seals and hook it back up. My guess is that the retaining clip has slipped off (red thing slids fwd and back to hold the retaining clips in place)