Fresh Water - Coming out of tank while towing

OK...on my last trip out, my sister followed us for the 5 hour drive. Once we got there she told me she thought she could see water coming from the trailer during the drive.

I filled the tank at home (dry camping...must fill before leaving) and I turned off the water once I heard some coming out of the overflow valve. Now...it continued to do this for a while, but stopped later on. I just figured it was "burbing" itself to a normal "full" level.

Once I got to camp, the gauge on the inside said I has 1/3 of a tank left....not good.

Not a drop of water in the basement area or coming from under the trailer...so that is fine...check a few times just to be safe.

Here is a picture of the overflow valve. I see that it is somewhat barbed, so that has me thinking there might have been a hose or something else there to stop water from coming out during travel. I'm sure water is sloshing all over in the tank during travel, but I wouldn't expect it to keep coming out of the overflow valve.

Ideas..???

Ah but it does. If you want to have a full tank of water upon arrival at your destination you need to add a short length of poly tubing (doesn't need to be pex) with a valve on the end.
Been there and experienced that!!!
https://www.amazon.com/gp/aw/d/B00C...stic+valve&dpPl=1&dpID=311KaIiakYL&ref=plSrch


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That is the way they come from the factory. There is another one on the other side of the trailer. These are the overflows as well as the vent for filling the tank. I installed a valve on each side to prevent the water from sloshing out. If you do this, you need to remember to open the valves to fill the tank and then close them for travel. You also need to open the valves prior to using the pump.

You'll want to put the valve on the end of both lines.
We have discussed this a few time on the forum.
I've have it on my to-do list but have done it yet. That is to find or make a valve to let air go in and out but close when the water hits it.
And typing this just gave me another idea.

Of course you'll fill your tank then let it settle and close the valves. But if your traveling up and down in elevation you will build positive and negative pressure in that tank that could maybe cause problems. Who knows.
Also when you get to camp you'll need to remember to open the valves before you start using the water pump.
Or you'll cause more problems.
All things to think of when you close up the vent line




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I wonder is just closing one side would greatly reduce the amount of water lost. If these vents are actually plumbed into each side of the tank then water can come out one while air goes in the other. Blocking one should reduce that somewhat. That's my theory of the day! Has anyone tried that?

In reality the vent lines need to loop much higher than they do today!

I would think that a valve on UDC side(open it while filling the tank) and on the other side an extended line going up behind the shower where vacuum break is for the black tank flush(it is MIA in the line) and back down to the vent hole in the UDC might work. Chris

We have an air vent next to the filler hole on the Prowler, plus it has the two over flows under the trailer like pictured above . . .

I've never pulled it with a full tank of water (usually only travel with enough water to flush the toidee and wash our hands a few times), so I've never experienced the splash out.

Since I do have the air vent by the filler hole I wonder if I could put valves on those over flows and just always leave them closed?

Look behind UDC...there is no vent line connected to the port on the backside of the Anderson valve on mine.

There was a very recent thread about this very topic and a search should turn it up. I have three over flow valves which I close once the tanks are filled. I have never seen or had an issue with positive/negative tank pressure and fill at 1400 feet and Camp at 8500 feet.

I do not believe that water expands much at altitude. Air does, so a full tank would be best. Chris