I have a 1999 rexhall 32 ft rexaire. While camping last weekend, a secutity person informed me I had a water leak ( california drought). At night couldn't find source, turned off water till morning. It seems there's no check valve where the fresh water goes into the holding tank.In checking around , talking to a M/H mechanic familiar with rexhall. They never installed a check valve at that point. Never got an answer to why this would start now. Have had M/H almost two years, no problems of this sort before. IE: The leak occurs when the fresh water tank is full, and leaks out the overflow valve.Sorry I'm so long winded and I will appreciate all your help. THANK YOU.

Many MHs have that same leak. Turn off the RV park water for a day or so and use the tank water. I never fill my on board fresh water tank until I am ready to leave. Are you sure it was your fresh water overflow? My A/C in the rear of the MH leaves a puddle in about the same area.

No check valve on the fresh water fill for the supply tank?Ok, first a question.. On most RV's that have a hose connection you can fill the fresh tank from the hose connection is the standard city water connection and that is checked.. The other connection is a gravity feed meaning it is ABOVE the top of the tank and it is not checked, it is also like 1.25 inches diamater (swimming pool vacuum hose size). Does your RV have a SEPERATE fill fitting? Or are you talking about the flush fitting for the black tanks?That one should have a vacuum breaker, well above the tank (often in the bathroom) and fresh water (only) will leak back when you disconnect. However only what is in the line up to the vacuum breaker.. From there on it's checked.If you have like a Tornado.. then there is a spring check in the tornado, but the supply line may leak back and due to the design of the line this may be slower.I have the tornado, but fed by the original vaccum broke line so,, Well, it's complex. (I like complex sometimes,, And the hose I feed it with has a second spring check and a second vacuum breaker,, Belt and suspenders yes. Effective yes. I'm not paranoid, Germs are out to get me... And you.. And everyone else.

If you are talking about the Gravity fill and then the small hose vent for that. The odds are you are siphoning the water out of the tank. some tanks do not have an adequate air intake and with no air in the tank you will gravity siphon the water out. Doug

Reduce the level in the tank. Once it starts, it's like a siphon.

Let's see if I've got this right. You are hooked up to city water and your water tank has filled itself and is now overflowing. Is this correct?If this is what is happening the most like cause is the check valve in the water pump. Lot's of things can cause this to happen - incoming water pressure is high and is forcing water past the valve, a bit of dirt has caused the valve to stick open, or maybe the valve has just worn out. Fixes are relatively simple - add a check valve between the tank and the pump inlet, rebuild the pump, or replace the pump.

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