Filling Water Tank

One solution I have though of is to extend the overflow tube up into the wet bay of mine so it is above the top of the tank. When it is full it will flow right back out the inlet for the water hose and cable.

I had this happen to me on my last 2 fivers... BOTH had a ball valve shut off installed on the drain hos to correct the issue..

I fill up with the valve open, Once the overflow starts flowing I shut the valve.

Once I get to where I am going, I open that valve,, A small amount of water that was in the hose drains out, but that's it.. Perhaps a gallon MAX...

I put a 1/4 turn valve on mine. Leave it open filling and when water comes out just close the value. Water would splash out the over flow while going down the road

I have just put a "wire nut" into the overflow tube after filling the fresh water tank. I used to lose a bunch of water before doing that. However, now I don't travel with much water at all and fill up at the campground when we get where we are going. The "wire nut" in the proper size worked very well.

I'v experianced this on our unit (only one of about 5 different rv's), seems to help if filled slowly. If filled fast, the overflow takes it down to about 60%.

GrumpyandGrandma wrote:
Happens with many units, the water siphons out. Some people install a valve on the overflow you just have to remember to open it when filling and after you arrive at your destination.

Yep! This is exactly what I did. before that, I'd lose a third of the freshwater driving. We only haul water when going to a non-F/H campground.

Fairly common problem. We had a motorhome that did this and my solution was to open up the fresh water tank drain line for a few seconds to break the vacuum and stop the shiphoning.

Is your overflow hose outlet above the top of the water tank? It should be.

Happens with many units, the water siphons out. Some people install a valve on the overflow you just have to remember to open it when filling and after you arrive at your destination.