2021 GT 7 Fresh Water Tank Siphoning out

[turnski10]

It seems ever time I drive our coach , mostly back and forth from the dealership for repairs, I've noticed that the fresh water tank siphons out while I drive. On our only trip since purchase I left with a full tank and got to our dry camp destination to find we had less than a third of a tank left. Left our selling dealer after some repairs on this issue and had them fill the tank for me to check the repair, on the 56 mile return trip to our house, it was again down to a 1/4 of a tank, I visually inspected and checked the digital reading inside to confirm. I also noted that the digital is way off, most likely needs calibration. Just wondering if any one else is having this same issue ?

[NXR]

Did you visually check the level before you left the dealer?

Do you travel with the water pump on or off? We never travel with it turned on.

Some of the later models actually have two fresh tanks. One is further forward and feeds the rear one. Do you know if yours is that way? Ours is not so I can offer no guesses on that configuration.

Do you have the slanted dash with the Sony radio up front or the non-slanted dash with the Jensen radio up front?

Forest River introduces major changes to their models halfway through a model year. The older design would be a, for example, 2021.0 while the updated one would be a 2021.5 yet both would show "2021" on the title.

The slanted dash and Sony radio were introduced with the 2021.5 model variant. I don't know when the "dual fresh tank" change was introduced, though.

Ray

[kenandterry]

I had the siphoning effect on our 2010 Georgetown if I had to fill the fresh water tank completely to maximize “dry camping” capacity. The siphoning starts with the water sloshing around inside and it can empty your freshwater tank.

I can’t find the very old post I made with my shut off tap in-line on the overflow line. I stole this photo below of exactly the same mod I made to stop from emptying the tank.

BEWARE!!!!!!!

Make sure to open the valve once you start using the fresh water tank via the onboard pump. It can cause suction damage to the plastic walls of the tank as you draw water from the tank.

[NXR]

Since the overflow is at the top of the tank, I've read of people just poking a small hole in the top of the "bend" to break the siphon.

Ray

[360true]

Well documented"fix" is to poke a hole in the top of the drain hose. 2x.

[cariboo camper]

Move the overflow pipe so that the end of the hose is not below the bottom of the tank , but is coiled up near the top of the tank. Do not know why but it worked for me. Actually I was so baffled by this I placed siphon hose back where it was and it again drained the tank. After repositioning the siphon hose near the top it quit draining the tank. Use zip ties to hold the hose up and just make sure that in the event of overfilling the water coming out does not soak anything that should not get wet.

[rk06382]

I was able to fix that problem. See thread:
FIX for "Fresh water tank self draining?"

I recently replaced the hose vacuum breaker with a backflush vacuum breaker valve at the top of the tank.