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Old 07-25-2011, 01:15 PM   #1
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Fresh water tank overflow

When I fill the fresh water tank on my Winnebago Vista 26P and it reaches full, it starts overflowing out the overflow tube and by gravity/suction, takes 12-15 gallons before it finishes overflowing. Even if I stop filling before full, when I start driving, the gravity/suction
effect takes 12-15 gallons off the top of the tank. Is it possible to plug the overflow tube or
is it needed for a venting effect on the system?

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Old 07-25-2011, 02:05 PM   #2
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My overflow is underneath the RV (03 H.R. Vacationer). Many times if I am going to be on the road for a few days without the benefit of an RV park, I will take the "rubber" nipple off of the bottom of the overflow pipe. There are threads there. I replace it with a galvanized cap and fill it up until I can tell the tanks are full at the "outside fillup location". But, I am very careful to monitor it so I won't have an overflow problem somewhere else. When I get to a site with amenities, I replace the rubber nipple.

Joe from Ct.
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Old 07-25-2011, 04:12 PM   #3
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Your tank needs a vent or the pump won't be able to suck water after a short while. Some tanks have a separate vent, but some rely on the overflow tube. All you can do it try.
Where does your overflow exit the coach? Is it possible to raise the end above the top of the tank to avoid the siphon action? One coach we had drained behind the rear cap, so the exit form the hose was way up high.
Gary Brinck
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Old 07-25-2011, 04:19 PM   #4
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If you can physically get to the overflow tube, you can put a T in it at its highest point, and add an open vent tube (smaller diameter) going straight up a foot or so. This will kill the siphoning action and won't interfere with the overflow tubes's ability to handle the overflow water
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Old 07-25-2011, 04:23 PM   #5
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YES, the siphon needs to be interupted. However, if you fill it up and some drain out, just add about 80% of that amount and you are good to go.
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Old 07-25-2011, 09:29 PM   #6
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Ours does the same thing. Also, if I filled until the 'full' light was on steady, water would siphon out if I parked on an angle with the tank on the low side. I started filling the tank just until the 'full' light started to flicker and stopped the fill...that seems to have helped on both counts. Bob
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Old 07-26-2011, 09:50 AM   #7
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Here is what I did. I have an extra day of water now when traveling - dry camping. BUT mske sure that they are open when filling or that you have a vent in the filler.
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