This subject came up in my mods. I installed a LiFePO4 battery inside which freed up the battery rack. I thought I might carry an extra tank there but found that there is insufficient vertical room for the tank. I remarked as such and Offgrid affirmed my conclusion.

Geewizard asked, "Why isn't it ok to carry a propane tank on it's side?" and remarked, "I have a horizontal 30 lb propane tank in my truck camper.  It has the same valve as any other propane tank."

My comment was, "If you look at both a standard tank that is meant to be carried upright and one that is meant to be carried horizontally, you will see that there is a difference in valve placement. For the propane tank to work properly, the valve must be above the liquid level so that vapor is drawn off to go through the system. A standard tank would have the valve below the liquid level when the tank is full. A horizontal tank has the valve offset so that when it is installed, the valve is above the liquid level. That is my understanding of why it is not okay to transport a standard 20lb cylinder on its side."

I think this is important enough to need its own topic. I also think this is something that should be part of a FAQ on safe transportation and use of propane.

I have looked at different LP tanks on Amazon, and see that some that look like converted vertical cylinders have the valve offset so that the valve would be above the liquid level when the tank is mounted horizontally. These appear to be suitable for use either vertically or horizontally. They need to be filled while in the vertical position.

True horizontal tanks are meant to be mounted in the horizontal position and not moved for filling. These may have the vapor valve at the same or a lower level than the fill valve, but there must be some sort of internal tube in a case like this so that only vapor will be drawn off and not liquid when these are properly filled and used. As I do not have one to cut apart and see how it is made internally, I must speculate, but think this is likely a good reflection of the actual construction. However, if someone has better information, please add it so this will be an accurate and more useful discussion.

Or, now that you have extra room, move the existing tank rack as far towards the body as possible, and see if you have room for an extra (3rd) tank on the A frame in front of them. Our current camper has this arraignment... Called "tri Five" by the manufacturer

Now I know why it is unsafe to transport or store 20 lb propane cylinders on their sides, especially if they are full enough so that the safety relief valve would be covered by liquid propane.

I might consider changing from a single-tank mount to a dual-tank mount now that I have made the changes. I don't think the tri Five would be workable for me.

 <<you always have to insert a smiley like this or SOMEBODY will take the joke seriously!

https://www.nfpa.org/Codes-and-Standards/All-Codes-and-Standards/Free-access - https://www.nfpa.org/Codes-and-Standards/All-Codes-and-Standards/Free-access

I did a quick scan and the only thing I saw that might be an issue with moving the propane cylinders back toward the trailer box is the requirement that the cylinder pressure relief outlet be a minimum of 3 feet from any appliance intake or exhaust port. So the water heater might possibly get too close. If it is you can pipe away the pressure relief vent. 

But you should probably read through the standard yourself, I didn't spend a lot of time scanning it. 

If you really need more propane, then you can get a 30# or a 40# tank.  They'll just be a little taller in the existing rack with no need to change anything, except, perhaps, for a little longer propane hose.

I wouldn't want a 30 lb tank personally because that would eliminate the option of swapping tanks out at a convenience store. The other solution is just to carry an additional 20lb tank in your tow vehicle. 

The Beauty of a truck... My spare tank is in the bed!

The only time I bought exchange tank propane was when I had a tank that was getting a little old and I wanted a newer tank.  I exchanged the old one for one that had a very recent date on it.  That exchange tank propane is pretty pricey, when you can to the local farm supply or rural gas station and get it for much less.  Too bad Gas Buddy doesn't list propane in its app.

As I travel, off the beaten path, I find less and less areas to re-fill. It's getting to the point of swap-out happens more often. 

I do carry my tank upright and have a spot in the bed (under the tonneau) sectioned for it, no chance of moving. I like having the spare (never know where or when you'll run out) and the time to re-fill as we travel through areas. A tank will last us 1-2 months of use depending on heater use. Meaning, I do run out somewhere on the road. 

Maybe it's an insurance thing, I don't know, but it's just harder to re-fill the tanks as we travel. Seems they've gone to swap-out...

Don't transport a propane tank in the horizontal position.  If the valve gets broken off it will become a rocket.  I used to lay one of those 30 gallon tanks down in the bed of a pickup to transport up to a fire lookout.  The propane guy warned me to be very careful doing that.  He said he saw one go through a cement block wall.

Originally posted by offgrid Consider converting your genny to propane if you carry more than one cylinder. I did that with my Honda and its great. No smell or mess, oil plugs and carb stay nice and clean too. The kits have a selector so you can always go back to gas if you want to. I never will.

I would like to do that but I did not see a conversion kit for a Generac iX2000. I'll have to look harder.