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Old 10-03-2018, 12:14 AM   #1
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Fresh water tank capacity & overflow?

I got this RV last February and used it until I came home in late March, then used it for one trip this summer. So I haven't filled the tank too many times. Today I had the bay door open so I could see the fresh water tank. I was filling the tank and standing next to it. When it was near full I went to the other side to be ready to shut the water off when the tank over-filled. It never over-flowed! I went back to the RH side of the coach where I could see the tank. To my surprise the top of the tank had expanded upwards 2-3 inches!!! I went back and turned the water off. Previously I had never viewed the tank but noticed when the water did overflow it flowed for a long time, several minutes. Which I'm guessing was siphoning the water out of the tank...????


I noticed the over-flow hose loops upward in the bay fairly high, several inches above the top of the tank, before turns and comes down the the floor of the bay. My questions are: has anyone noticed the tank expansion?
And, has anyone lowered the height of the upward loop of the over-flow hose?


The enormous tank expansion concerns me. I couldn't see my fresh water tanks on my previous motorhomes, so maybe they all expand?????
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Old 10-03-2018, 03:33 AM   #2
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Yes, I've seen it expand. No need to panic. If you overfill the inflow is more than the (2 on mine) vents can handle. Shut off the hose and it will return to normal.

And yes, you can syphon out trough the vents and end up with 85% or so of tank filled. I've also had it happen once when I was parked for a few minutes at a lateral angle and somehow the syphoning got going.

I would not lower them as that would increase syphoning odds.

RKNOLA on this forum made an anti syphon valve out of Home Depot parts if this is a concern to you.
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Old 10-08-2018, 01:17 PM   #3
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Draining water from bottom of the tank

In addition to stopping the siphoning that prevents water from staying in the top of the tank, I've devised a hoover-style pickup that gets water from the bottom of the tank. I discuss it at
http://www.forestriverforums.com/for...nk-142357.html

Overall, I've probably recovered 25% or more of the capacity of my water tank.

–Gordon
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Old 10-30-2018, 09:46 AM   #4
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Made an anti-syphon device for fresh water tank

I made one of these for my open-loop geo-thermal heating used water drain system for my house and it works great.



I'll admit I haven't filled my water tank since installing, but feel confident.
I thought I'd attach a photo so the next person could get some ideas on their own.
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Old 10-31-2018, 10:02 AM   #5
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Overfilling the water tank will probably not burst it, as long as there is a vent. Yes indeed, as it has happened to me, overfilling turns the rectangular tank into a pillow shape. When this happened to me, I was shocked at the fact that the square edges of the tank raised above the low metal bracket screwed to the floor and meant to keep the tank in place. Since the overfilled tank weighs hundreds of pounds, I feel that a hard panic stop of the moving motorhome can cause the tank to slide over top the bracket and possibly burst the tank. I haven't heard of this happening, but I believe the possibility is real and everyone should be aware of that possibility. Perhaps newer Berks have a better method for corralling the tank.
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Old 10-31-2018, 03:06 PM   #6
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Quote:
Originally Posted by I-RV View Post
Overfilling the water tank will probably not burst it, as long as there is a vent. Yes indeed, as it has happened to me, overfilling turns the rectangular tank into a pillow shape. When this happened to me, I was shocked at the fact that the square edges of the tank raised above the low metal bracket screwed to the floor and meant to keep the tank in place. Since the overfilled tank weighs hundreds of pounds, I feel that a hard panic stop of the moving motorhome can cause the tank to slide over top the bracket and possibly burst the tank. I haven't heard of this happening, but I believe the possibility is real and everyone should be aware of that possibility. Perhaps newer Berks have a better method for corralling the tank.
Don't go driving until it's "deflated". And to be exact, the (over) full tank weighs north of 850 pounds.
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Old 10-31-2018, 09:51 PM   #7
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I stopped the syphoning when filling and driving by drilling 2 small holes in the top of the vent loop. This lets it suck air in instead of syphoning the tank. I will admit watching the tank swell like it does is pretty nerve racking.
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Old 10-31-2018, 10:13 PM   #8
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Quote:
Originally Posted by rte154 View Post
I stopped the syphoning when filling and driving by drilling 2 small holes in the top of the vent loop. This lets it suck air in instead of syphoning the tank. I will admit watching the tank swell like it does is pretty nerve racking.
You know, I will do that first thing in the morning. Brilliant. Worst thing that can happen is that you get a few drops when you overfill.... so what. Thanks!
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