Increase Your Truck's Range and Cure Range Anxiety: RDS Auxiliary Tank & Toolbox Installation 

I have received several questions around concerns that the aux tank will cause the main tank to overflow through the main filler tube when both tanks are open,. I can assure you that this is not the case. I have had both tanks completely full with the shut-off valve open. I have let the truck sit for several weeks with both tanks full, less the short drive back from the filling station, and I have had no leaks or overflows. Here is the reason why they do not overflow. The reason the main tank is not overflowing when the auxiliary tank is also full is due to a principle in fluid dynamics known as hydrostatic equilibrium. In simple terms, two connected containers of fluid will eventually balance out to the same level, regardless of the size or shape of the containers. This is why water in a series of interconnected tubes or vessels all settles at the same height. In the case of this install, when both the main and auxiliary fuel tanks are full and the shut-off valve is open, the fuel in the auxiliary tank will flow into the main tank until the fuel levels in both tanks balance out. Since the T-connector is about a foot below the auxiliary tank, the fuel can only flow into the main tank up to the level of this T-connector. Imagine a long straw with both ends open. If you submerge one end of the straw into a cup of water, the water will rise in the straw only to the level of the water in the cup, not higher. It's the same concept with these fuel tanks. When using fuel from the main tank (while driving, for example), the level in the main tank will drop below the level of the auxiliary tank's T-connector. The auxiliary tank will then start to drain into the main tank to equalize the levels until the fuel level is once again at the height of the T-connector. If the main tank fuel is used so the level in the main tank drops below the T-connector, the auxiliary tank will continue to drain until its level is at the T-connector or until the main tank is full, whichever comes first. If the fuel consumption continues and the level in the main tank falls below the T-connector, the auxiliary tank will continue to drain until it's empty or the main tank is full. If the main tank is full, it won't overflow because the fuel level in the auxiliary tank is now lower than the T-connector, and the auxiliary tank cannot push more fuel into the main tank. Therefore, as long as the level of your T-connector is below the maximum fill height of your main tank, you shouldn't experience an overflow from the auxiliary tank into the main tank. Oh but wait....The T-Connector is above the top of the main fuel tank..... Yes that is true, but...... If the T-connector is above the main tank but below the maximum height of the fill tube that fills the main tank, the fill tube effectively acts as part of the main tank for the purposes of balancing the fluid levels. As such, the system will still balance out to prevent overflowing. Here's why: the fill tube for the main tank, as long as it is open to the main tank and not obstructed, is considered as part of the "volume" of the main tank. Fuel will rise in this tube up to the level of the T-connector, the same way it would in the main tank itself. Fuel will flow from the auxiliary tank into the main tank and its fill tube up to the height of the T-connector, balancing out the fuel levels. So, even if the main tank's top is below the T-connector, the fill tube's extra height provides the space needed to prevent overflow. However, this can depend on the specific setup and design of your fuel tanks, so it's always a good idea to consult with a professional or the tank's manufacturer if you have doubts or questions.

You're the best. I think this is one of the most informative videos on this matter, out there. Nice job. Thanks for posting this video.

We at Tank and Barrel loved watching your detailed video and how it turned out! Thank you for sharing this. We're glad you're happy with your purchase!

Another great video scott! Love the upgrade too. That’s going to be a huge help for you on trips. Ok, Let’s go!!

This is on my list as well. Great content and great details on how its done!

Doing this with a 91 gallon combo soon Thanks for the detailed install

Nothing wrong with being meticulous and slow. Measure twice cut once eh? Fabulous job by the way. I can’t believe Ram wasn’t going to warranty a 50 gallon tank that comes from their factory. Very odd! I’ve been looking at one of these vs a 50 gallon upgrade tank under the truck for my 16’ Ram Laramie. Still checking things out. Thanks for the video!

Nicely done. Thank you for taking the time. We will be checking out ”Tank & Barrel". Maybe see ya on the road sometime, be well and safe travels.

You should be spraying that grommet down with rattle can bedliner before and after installation.

Does rds not supply spacers for under the mounting tabs? Seems like a point of failure being mounted on an unsupported tab…. A lot of other manufactures supply spacers for areas of the mounts that don’t touch the bed directly

Where did you get the bolts and springs? What size bolt and nut?

How hard is it to fill your new tank when your fifthwheel is attached?

Does the fuel shut off once the main tank is full? i thought that there would be a check valve somewhere inline ?

What keeps it from over filling the truck tank? Do you need a cut off switch?

Silly intro.