Too many drains?

[NW Snowbirds]

So I filled the fresh water tank today for the first time. Actually over filled it. Water came out of the overflow drain line as expected and continued to flow until the fill pipe was empty. But another blue drain beneath the trailer continued flowing for a considerable time - perhaps 15 minutes. The tank gauge indicated full directly after filling . After the blue drain pipe stopped flowing the tank gauge showed only two thirds full. So what is this extra blue drain pipe exiting beneath? There are 5 drains. Hot water line (with valve at the terminus), cold water line with valve, fresh water tank drain line with valve, white overflow line (no valve) and blue line (no valve).

[atom ant]

Ah - the mystery line. Several have had the issue with it. As I understand, once the water flow starts through it, siphoning starts and you cant stop it. I may valve mine and just open it when I fill the tank.

[Dave&Ginny]

Yes several of us had that problem.....the factory corrected that on the newer coaches. Take it to your dealer (so they can fix it) or cap it and do as Brad had posted above.

[SueMar]

Thought it was a line to let air into the tank when you're using water. If you don't let air in,the water pump keeps pulling water out and the tank collapses (or at least could) because a vacuum is created. The problem with the older models was that it was located too low, allowing it to have a siphon effect. If I recall, the solution was to have it raised up sotheincoming water wouldn't siphon out of the tank.

[atom ant]

Hmmm, maybe mine was already corrected at the factory. I've never filled the tank yet.

[Dave&Ginny]

Originally Posted by SueMar

Thought it was a line to let air into the tank when you're using water.Â* If you don't let air in,Â*the water pump keeps pulling water out and the tank collapses (or at least could) because a vacuum is created.Â* The problem with the older models was that it was located too low, allowing it to have a siphon effect.Â* If I recall, the solution was to have it raised up soÂ*theÂ*incoming water wouldn't siphon out of the tank.Â*Â*

there are other vents so this isn't a problemEdited by: Dave&Ginny

[NW Snowbirds]

The answer from the factory is that it is a vent line to keep from developing a vacuum when drawing water out of the tank and subsequently collapsing the tank. They confirmed that the line siphons water out of the tank until the level is below the lowest vent line terminus inside of the tank. They suggested the way to get a 100% fill is to watch the tank level on the inside gauge and then shut off the water when it just reads full. Doesn't completely make sense to me since there is already a white overfill/overflow line out the top of the tank which goes overboard. It would seem as though the overflow line would admit or discharge air acting as a vent. Maybe some day I will open the bottom panels to see how these lines are routed