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Old 08-13-2015, 02:32 PM   #1
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Location: Mount Laurel, NJ
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If You Want More Fresh Water

If your fresh water tank is connected like mine, the bottom 25 gallons cannot be used because the pump starts sucking air (see photos). This means we are carrying around 208 useless weight.

To get more water into the tank, you can fill it to the "F" light comes on, but this is only 83 gallons and with the bottom 25 gallons being useless, you have 58 gallons to use.

Next you can crawl down on the ground to take those blasted pins out of the latches to watch the tank fill. Now you have 75 useable gallons.

Rather then deal with those latches, I once just filled the tank until I saw water coming out of the overflow, beneath the RV. I shut the water off and was amazed that water kept coming out for several minutes. I quickly found out that the overflow siphoned the top 21 gallons out, leaving me with 79 gallons and 54 useable.

Well where is this going??? I cut 7 1/2 inches of the overflow tube off (from the floor up) that protrudes through the floor. Enlarged the hole (with rat tail file) for a 3/4" PVC pipe. stuck the cut overflow tube into it and hung it with a tie-wrap. Tried to use few tools.

Now the tank can blindly be filled until water comes out the tube. Then when the water is shut off, there will be no siphoning action. You will have 100 gallons with 75 useable.

I know that many do not want to carry 100 gallons, but for those that do, here is a filling method.
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Gale & Hank- 2012 Berkshire 390BH
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Old 08-13-2015, 03:01 PM   #2
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You are a genius!

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Old 08-13-2015, 03:17 PM   #3
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Interesting, not had mine long but have normally used the fill up till overflowing method. Didn't realise I was losing that much water. Will have to open that side up and have a look now. Thanks.
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Old 08-13-2015, 04:44 PM   #4
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Thanks. Great info.
2014 Berkshire 390RB-60
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Old 08-13-2015, 05:20 PM   #5
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Location: In our coach
Posts: 230
Now I know why mine kept draining after filling to much, couldn't figure out why it didn't just drain down a little.
You are a smart cookie to figure that out I-RV! Well definitely do that mod soon.
Ben & Michelle
2015 Berkshire 38A
2005 Jeep Wrangler toad
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Old 08-13-2015, 08:01 PM   #6
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Brilliant, thanks!
2008 Berkshire 360QS-40
"If you can't fix it with a hammer, you have an electrical problem"
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Old 08-13-2015, 08:05 PM   #7
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Fantastic! Thanks for sharing!

2016 38a
2016 38a
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Old 08-13-2015, 09:51 PM   #8
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I'll be doing mine soon. Thanks!
2011 Berkshire 390-rb-40, upgraded tires and front axle airbags, 2012 Jeep Wrangler 2 door, Blue Ox baseplate and BlueOx aladdin tow bar, Blue Ox Patriot brake system, wiring run through right frame rail and homemade led taillight bar.FB.
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Old 08-14-2015, 11:09 AM   #9
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Nice mod.

For those who will not try this, you can see your FW tank level from the DS wet bay. It's right behind the sewer and gray dump valves.
2013 Berkshire 390BH
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Old 08-14-2015, 01:25 PM   #10
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Well done ... let me guess, an engineer?

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fresh water, water

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