Problem with Water Tank Vents

[ssullivan]

Does anyone have any information how water tank vent lines are normally set up on cats?

Mine are set up internally, rather than going to a thru hull vent near the hull/deck joint. They are looped up toward the hull/deck joint and then lead back down again to the bilge to overflow into the bilge.

The problem is:

When we are moving, the boat seems to be sloshing the water in the tanks around enough to cause water to go up the vent tube and end up in my bilge. This is our *fresh* drinking water and we live aboard away from docks, so we cannot have this type of thing happening. Every drop is precious.

1) How do cats normally handle this issue? If I had it going to a thru-hull at the hull/deck joint, it would be spraying out to the sea instead of the bilge. How can I stop this?

2) Monos tend to have more distance from the tank to the hull/deck joint than my catalac does. I only have a about 4 ft to that location from the tank. It's not providing enough distance (vertically) to keep the water in the tank when we start moving around in a seaway. What are common solutions to this problem?

Thank in advance for any design ideas.