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Old 06-02-2015, 10:06 AM   #1
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Freshwater Overflow questions

Because I was losing about 1/3 of my freshwater out of the overflow tubes while traveling, I added valves on the overflow tubes. I know this is a common issue/solution, but I have some questions.

How I understand it: I am supposed to fill the fresh water tank and close the valves. Make sure to open the valves when I arrive at camp. This is supposed to keep me from losing a lot of water while driving. The problem is that once I get to camp and level, when I open the valves, I still lose a ton of water. It just seems to siphon out.

This last weekend, I left the valves closed while I camped (I DO have a vent line connected that goes from the gravity water fill to the tanks). A number of times, I cracked open the overflow valves to see if using water with the valves closed created a vacuum in the tanks. I figured that if it was creating a vacuum, instead of water coming out of the tubes when I opened the valves, there would be an inrush of air. This never happened. Even after using water all weekend and taking two showers, whenever I opened the overflow valves, water would still come out.

My question is do I really need to have the valves open while at camp or will the vent line from the gravity fill to the tanks keep the tanks vented. Do I only need to open the valves while filling the tanks? I don't want to damage anything, but also want to be able to use all of my water. My old 2000 Jayco didn't have this problem... Thanks.

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Old 06-02-2015, 12:39 PM   #2
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I'm interested in this as well.Filled my tank and was at 2/3 when I got to the camp site.

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Old 06-02-2015, 01:51 PM   #3
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Because of the forward movement and braking, water will be lost through the overflow lines. If they would have them installed the same height as the FW tank fill then the problem would be solved (as far I can see).
The overflow lines come from the top of the tank as do the FW inlet and FW inlet vent.
A proper solution would be a place where you could install a 30" psc. 1-1/4 or 1-1/2" abs drain pipe upright in a closet through the floor so when the hoses are extended and installed in this drain pipe it still could be used as overflow. On top of the abs drain pipe put a cap.
To put valves on the overflow hoses is generally not a good idea. You might forget and pressure might built up and rupture the FW tank.
Because I have to same problem as many others do, this will be my next mod
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Old 06-02-2015, 06:12 PM   #4
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As long as there is a vent in the gravity fill, then I am not sure pressure can build in the tank. That is assuming that the gravity vent doesn't have some type of back flow prevention.
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