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Discussion Starter #1
I recently purchased an auxiliary fuel tank install kit and wanted to let you know my findings so far. The anti-rollover valve is just that. It does not shut off the fuel when the fuel level gets to that level. This valve is only to stop the flow from the fuel tank to the auxiliary fuel tank. Upon messaging the manufacturer of the rollover valve they confirmed this.
I have dismantled the roll-over valve to show you what it entails.
However, the filler neck check valve may stop the flow of fuel out of the fill neck. I will update the post after the rain stops in a few days.

Has anyone tested this theory? Had a full tank of fuel in the main tank, then turned on the auxiliary fuel tank and did it overflow?




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Mine has a similar looking valve where the fuel tees into the filler neck hose. My auxiliary tank valve has been open since April and never leaked a drop out the main filler neck so apparently it does it’s job just as it’s intended. It gravity feeds from the auxiliary into the main and this valve stops the flow before it gets high enough to run out the filler neck.
 

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Never had an issue with my float valve either. I installed mine in the rubber hose between the metal filler neck on the tank. It was more of a hassle, but worth it to me. The float valve is now completely vertical.
 
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Never had an issue with my float valve either. I installed mine in the rubber hose between the metal filler neck on the tank. It was more of a hassle, but worth it to me. The float valve is now completely vertical.
That's how I installed mine too.
 

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Discussion Starter #5 (Edited)
Do me a favor, with your main tank full and your auxiliary tank filling the main tank, go and push the fuel fill check valve past the flapper down. If there is fuel there I will go ahead and install my valve. If not I will look for a "better" valve.
What brand did you guys use?
I used southern truck but they all seem to use the same valve.

I have uploaded a video of my test of the valve on youtube check it out and tell me what you think

Honestly, I am not surprised because if you calculate the PSI of the tank it makes sense. If the valve is 12" below the bottom of the auxiliary tank, and the tank is 24" tall then there would be about 1.3 PSI (3'x0.433=1.299psi) which would require a float of around 14 cubic inches or 2.5inx2.5inx2.5in cube to shut off the fuel if my math is correct.


 

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I'm using an RDS filler assembly with the same check valve mounted vertically. Tested same last week and no overflow. I don’t think it's a "rollover" valve. It serves as a check valve when it's floated upwards.
You could easily test the function by screwing the valve into a vented pvc pipe. With the vent higher than the check valve. Turn turn on the fuel and see what happens.
There's probably a limit to the fuel 'head'. A 1' drop doesn't create much pressure.


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Discussion Starter #9
I'm using an RDS filler assembly with the same check valve mounted vertically. Tested same last week and no overflow. I don’t think it's a "rollover" valve. It serves as a check valve when it's floated upwards.
You could easily test the function by screwing the valve into a vented pvc pipe. With the vent higher than the check valve. Turn turn on the fuel and see what happens.
There's probably a limit to the fuel 'head'. A 1' drop doesn't create much pressure.


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Do you have a video of your test? How does a vented PVC hose change the test? I am just curious.
 

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Discussion Starter #10
I'm using an RDS filler assembly with the same check valve mounted vertically. Tested same last week and no overflow. I don’t think it's a "rollover" valve. It serves as a check valve when it's floated upwards.
You could easily test the function by screwing the valve into a vented pvc pipe. With the vent higher than the check valve. Turn turn on the fuel and see what happens.
There's probably a limit to the fuel 'head'. A 1' drop doesn't create much pressure.


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As you mentioned I attempted the same test with a vented PVC pipe with the same results. Even southern truck said, "The ball valve in the tee is precisely for roll-over only so the flow will never stop" unless the filler neck valve stops it. Which from all of the comments here (thank you) it seems that most valves do hold. Check out the new test here
 
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That is good to know Thanks for checking with the company. I may keep the valve closed more often...
 

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They seem to work. Thousands of gallons of diesel would be on the ground ny now if that check valve didn't work. I generally turn the supply valve off, but....? I would guess that more than a few check valves are incorrectly installed, the results thereof, keeps this discussion active..?
Great video! I like 'scientific proof'.

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I installed mine on April 4th and since then I have used 958.783 gallons of fuel without a single drop overflowing.

Still, if you're not comfortable with the system then it's not for you. I have a good friend who doesn't trust them so he runs an electric transfer pump.
 

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I'm good with it as is. Don't want a transfer pump. Want it stupid simple.
Had a transfer pump on a Ford that failed at the most inopportune time.


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Discussion Starter #15
I installed mine on April 4th and since then I have used 958.783 gallons of fuel without a single drop overflowing.

Still, if you're not comfortable with the system then it's not for you. I have a good friend who doesn't trust them so he runs an electric transfer pump.

Oh no. I completely agree simple is better. Thank you for the real world knowledge. This information is what I wanted to know. 1000 miles of no overflow means something is working. I have a 12 hour drive with a 5er coming up and did not want to have to keep getting out and opening the valve and closing it when it got full. It sounds like the filler neck valve will prevent it from overflowing.

When I bought the auxillary install tank kit I was under the impression that it came with a float valve to shut off the fuel when the fuel reached that valve. When I saw the tiny little float in there I knew it would not stop that. Instead of spilling my raw opinion I made a video of HOW I made my conclusion. I even did the math to confirm my conclusion. Then people like you come in and give real world info to reassure us that the filler neck valve must work to keep it from over flowing.

After I fill the tank up I will then test to see if the fuel rises to the first and or second valve in our filler neck and report back.
 
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