Peggy, thank you so much for the input. Actually, on the previous boats I did the vent lines and vents myself. The setups that were on the boats were bizarre at best and needed help. Now that you brought this up, I will need to get in the engine compartment with my trouble light and take a good look see at what we have. The only thing I can tell you is that there is a fuel tank looking vent fitting on that portion of the hull. I "assume" that it is for the holding tank, is actually hooked up and not blocked by something. It never occured to me that a vent was required for anything other than keepingthe tank from colapsing when you used the pump out.