water ballast maintenance and use

I am flying a pik 20b and am curious about using water. The ship has bags in the wings but no plumbing in the fuselage. The tray behind the head rest has no holes to indicate plumbing was ever there. There is a short section of hose connected to the drain hole in the bottom of the fuse but it is connected to nothing on the other end. The bags have a vent fitting but not to sure were they should be plumbed to. I am also curious about the water that does not completely drain from the bags. Do the bags become moldy after time? Do they need to be removed ocassionaly to get them completely dried out?
When useing water is it ok to partially fill the bags? Looks like water could move somewhat from inbd to outbd? Does anyone know where I might be able to get the drain valve I would need to set this thing up? Any comments would be appreciated.

Joe

Joe, I have read about people owning this type and having this problem. I also read that most have changed the bags to "Smiley" rubber bladders.