Fresh water tank concern

[Chucksands77]

Filled my Winnebago 37F and it over filled and water was pouring out from somewhere. Fried said they have an over-flow valve and that no harm done so we went forward using the fresh stored water and city water when parked. Weeks later i saw the fresh water tank was down to 1/3 so I filled it again and this time watched the tank reading while filling and shut off water as soon as full.....since that time I have lost 1/3 of water and have a fairly significant dripping coming from the fresh water tank area. No water pump running and still dripping and loosing water.....any suggestions or comments welcome. I am worried that I blew something apart when I over filled.

 

[SargeW]

Odds are it is just your overflow hose at the top of the tank dripping out. Crawl under it and locate the overflow hose. It often starts to siphon when the tank is all the way full and pressure pushes water out of the overflow. Once it starts it can keep running out until pressure equalizes in the tank. In one RV I had, I had to put a valve in the overflow to keep it from losing water after the fill. I would open the valve for during the fill, then close it after it was full.

 

[Chucksands77]

Thanks SargeW....if you are correct....that would be a huge relief. I wonder if leaving the fill door open for a few minutes would prevent it from syphoning out the over flow.?? Any other input is appreciated by all.

 

[garyb1st]

Could also be the fresh water drain. My fresh water tank drain valve is pretty hard to turn and will leak if not turned completely off.

 

[SargeW]

It's worth a try. And Gary's solution is a possibility as well. Either way, a trip under it while it's full of water should shed some light on the problem.

 

[John Canfield]

Every time I overfilled my tank, the excess water overflowed into the basement area. Fortunately I caught it before it was serious. Since then I now open the gravity fill cover so water would overflow out of it.

I had a mysterious water leak underneath the Horizon a few years ago and it was the fresh water drain valve not sealing, so that's another place to check for leaks.

 

[Gary RV_Wizard]

I wonder if leaving the fill door open for a few minutes would prevent it from syphoning out the over flow.??

"Leaving the door open" won't stop the siphon action - the surface air pressure in the tank is not what causes siphon flow. Besides, the fresh tank is already vented for normal operation.

Odds are the suggestions from the others will solve your problem. An actual leak in the tank itself is possible, but the other two items are much more common.

 

[Chucksands77]

Gary, Marty, & John, very much appreciate your input. !! Called Winnebago customer help desh today and the gentleman seemed to point towards a faulty valve. He directed me to their 3D virtual schematics and so I could really spin the plumbing design around and see how the plumbing is configured. Hoping to remove a panel on the drivers side compartment and take a closer look at the plumbing around the fresh water tanks. Hoping it is NOT a split open tank. !!

Really enjoying the forum here. Very informative and the advice is great. Even for a seasoned camper and now RV'er, one can always learn. All The Best To You All !

 

[Ray-IN]

Overflow outlets on tanks do not extend to the bottom of the tank, they are merely an opening at/near the top of the tank for an overflow condition as these tanks are not designed for pressurization.. A siphon effect would be highly unlikely.

And yes they can be pressurized with a city water fill connection @ 60-80 psi trying to overflow through a 3/8" overflow tube.

 

[Gary RV_Wizard]

Overflow outlets on tanks do not extend to the bottom of the tank, they are merely an opening at/near the top of the tank for an overflow condition as these tanks are not designed for pressurization.. A siphon effect would be highly unlikely.

If properly plumbed, I would agree. Sadly, there are more than a few Rvs out there that have vent or overflow tubes plumbed with the outlet below the inlet at the tank end. In theory an overflow tube can be inserted anywhere in the tank wall as long as the outlet tube is above the top of the tank, but if the outlet end is low and the inlet not high on the tank, then a siphon forms easily and keeps on running until the inlet sucks only air (near empties the tank). It happens often enough to be a well-known problem to those who hang around here and see a lot of trouble reports.