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Old 06-10-2015, 05:29 PM   #1
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Fresh water tank

Does your fresh water tank inflate when you fill it? My tank appears to bulge the top of the tank when i fill it. I'm wondering if my vent is blocked.

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Old 06-10-2015, 05:41 PM   #2
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I had the same problem! It all depends on the way it's filled from my perspective. I filled it once with 270 degree adapter and guess it put a lot of air in the tank. Recently, I removed the adapter and hooked the hose up directly. Checked the tank afterwards and no bulging. Hopefully this makes sense.


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Old 06-10-2015, 06:06 PM   #3
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Mine always bulges up. I figured I was getting extra capacity. I don't know if it's right or wrong but it has always done it.
Phil and Dianna
2011 Berkshire 390 RB
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Old 06-10-2015, 06:46 PM   #4
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I was sanitizing the system to get back on the road and when I went to the bay the tank was expanded to where it was touching the black and gray water tank. When I drained it it went back to almost level. I was worried it was just mine.
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Old 06-10-2015, 07:15 PM   #5
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Mine does it too, when I dry camp I actually let it fill all the way until it comes out the overfill/air vent.

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Old 06-11-2015, 06:05 AM   #6
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Add me to the list. Mine did it, but I tried filling it slowly the last time and no air bubble.
Unfortunately, I have discovered I have a small leak in either the tank or one of the lines between them.
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Old 06-11-2015, 06:32 AM   #7
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X2 on the bulging tank. My tank has a overflow hose attached about 80% up on the side wall of the tank. The hose turns up and then makes a loop downward and pokes through the compartment floor. When the water reaches the outlet fitting (80%full), water does not come out the overflow. But when the water bulges the tank and reaches the top of the overflow loop, siphoning starts and the water continues to drain until it goes below the drain fitting. I was startled once when filling my tank and not paying too much attention; I saw water coming out the overflow. So I shut the water off and then why water kept pouring out the overflow. I then investigated and saw where the top 20 gallons siphoned out - LOL!!!

Another problem is that the hose fitting to the pump is about 20% up on the sidewall. This is a very poor design. It means that you need to carry that bottom water around all the time and not be able to use it. This means that because of the design, 167 lbs. of unusable water is being carried.

A more vertical tank with a bottom outlet would be a better design, such as in my previous class-C.
Gale & Hank- 2012 Berkshire 390BH
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Old 06-11-2015, 11:28 AM   #8
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Same here, bulges when filled all the way. It's not a problem or concern if it's not leaking. My over fill line is not clogged.
2013 Berkshire 390BH
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Old 06-12-2015, 01:10 PM   #9
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I experimented while i was flushing my tanks. I found if I don't turn the pump on and open one faucet the tank doesn't bulge when it is filled and water doesn't come out of the faucet while filling. I just thought you guys would like to know.
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Old 06-12-2015, 02:28 PM   #10
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I have always watched my closely and stopped right before it got to the top. I didn't know what would happen after that.

2014 Berkshire 390RB-60
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