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FYI Siphon problems in a Newmar Class A Motorhome

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Staff member
RVF Administrator
Jul 27, 2019
Midlothian, VA
RV Year
RV Make
RV Model
Ventana 4037
RV Length
40' 10"
Freightliner XCR
Cummins 400 HP
2017 Chevy Colorado
I believe this issue is resolved in 2020's but prior years such as my 2017 had a production issue where they took a flexible line from the top vent of the tank and went direct from that point down to the exit. There was no arc above the tank. As a result when your coach is not level the water will pour out like a cup being tilted. We saw this in several Newmar's at the recent balloon fiesta with 1/3rd of their fresh tank emptying onto the parking lot which had a severe tilt where we had to disconnect the toads.

I experienced this at a campground where I filled my fresh at a location as the site didn't have water then drove down hill to the dump station, I don't recall much of an angle but I think the nose down got the water flowing out and I lost probably 40% of my fresh. As I visited Newmar for warranty work later I reported this. There fix was super easy. The flex hose that Nemwar used at production they just took a length that they could arc up I'd guess about a foot above the tank then down to the vent. I've seen all kinds of concoctions for a fix from vents etc. but it seems this super simple fix of not allowing water to just pour out of the top and over and down works. At the balloon fiesta I manually filled to 96% and lost none in the same tilt as others.

As I mentioned to our gang going to the balloon fiesta that you should manually fill your fresh tank as autofill does not get you as high as you want when you have to boondock for 5 days. I also mentioned that you should test to ensure you don't have the siphon problem prior to arrival so practice a few manual fills and go to a few campgrounds before you have to rely on this when boondocking. When I know I'm going some place with no water I will do a manual fill and observe the water level in fresh to be just below the fill valve which you can view from the wet bay looking under the wet bay board.
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