Thread: LP Gas Tank Installation

Is there a code that prohibits a propane gas tank from pointing at the structure. I could have sworn I had something on this but cannot find it. I called it on a home today and the seller's propane supplier says that it does not matter which direction the ends are pointing.

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I thought I saw something about this on here before but can't find anything.

NFPA 58 can be viewed on-line. Visit NFPA.org, click on List of Codes and Standards, scroll down to NFPA 58 and review. Here is a direct link to the 2011 edition.

http://www.nfpa.org/aboutthecodes/Ab....asp?DocNum=58

If you're looking at the current edition, start with chapter 6 (when the document loads in the real viewer window, click on "TOC" for an interactive jump list to the chapters.


You might also check what your local codes and fire suppression review for the property/neighborhood density, etc. have to say on the subject.

pointing is impolite, but not a fire code violation.

I see no cause for alarm there. Those tanks are often leased from the supplier, so that is where they chose to locate the tank, accessible for filling, at a proper distance.

I guess I must have dreamed it or something. There must be something to it though, because you almost never see them pointed at the structure. At least not around here.

The usual reason, probably (as I am guessing as to the usual reason), is one of clearances from the structure and the property line.

With the tank turned parallel with the house and the property line, less land will meet the required clearances as the tank is 'shorter' when installed parallel with the house and property line.

In this case, where there may be a larger yard area, they may have wanted to 'see' less of the tank looking out the windows, so the tank was installed perpendicular to the house wall to present a smaller profile when viewed from the house.

Originally Posted by brian schmitt

pointing is impolite, but not a fire code violation.

Besides, how do you know it isn't pointing away from the structure?
Some of the older tanks used to be "end fill" with the valve on one end, maybe these couldn't be pointed at the house??

I've heard this too so I called my local LP supplier about this awhile back.

I was told that yes, some towns do require that either end of the horizontal cylinder type LP tanks do not point directly at any dwelling. The reason given to me was that if the tanks rupture the end caps can blow off and become a projectile.

Yes, that is what I have always heard. The ends will shoot out like a bullet, thus they should not be pointed at the structure from either end.

Originally Posted by Frank Bombardiere

Yes, that is what I have always heard. The ends will shoot out like a bullet, thus they should not be pointed at the structure from either end.

You would not want the house damaged before the fire starts.

Originally Posted by Garry Sorrells

You would not want the house damaged before the fire starts.

If the tank explodes, the fire is already well underway!

Originally Posted by Frank Bombardiere

Yes, that is what I have always heard. The ends will shoot out like a bullet, thus they should not be pointed at the structure from either end.

That makes sense. We know water heaters tend to blow at the ends. Sounds like the Mythbusters need to blow up a Fat Boy full of propane.

Tanks have pressure relief valves so they vent upwards. If there is a fire, you will have one heckova blowtorch but it sill simply burn itself out after awhile. I've watched many tanks do this from house fires.

The only real danger is from a BLEVE-Boiling Liquid Expanding Vapor Explosion. Just Google it for videos. If you have a flame impinging on the tank at or below the liquid level, it will simply vent as above. However, if you have a flame impinging at the upper part of the tank, it will create enormous pressure while weakening the tank. When the upper tank ruptures at the point of impingement, you have a massive fireball the size of a city block. Note it blows out at the site of impingement-it doesn't blow out the ends every time. In fact, the ends are much stronger than the top of the cylinder. Now, when LP gas boils at -44F, it expands 277 times so you get an impressive little fireball.

If this theory about the ends of LP tanks being so dangerous then why don't they make bobtail delivery trucks with cylinders pointed to the sky and roadway? Does this mean you are in danger of following right behind these trucks? This is silly. Sorry,

From a physics stand point ..... If the tank was completely without safety features and the pressure was such that the tank would rupture, by design and shape of this vessel, it would rupture along the seam of the cylinder -- NOT the end caps.

Originally Posted by Bob Harper

Tanks have pressure relief valves so they vent upwards. If there is a fire, you will have one heckova blowtorch but it sill simply burn itself out after awhile. I've watched many tanks do this from house fires.

The only real danger is from a BLEVE-Boiling Liquid Expanding Vapor Explosion. Just Google it for videos. If you have a flame impinging on the tank at or below the liquid level, it will simply vent as above. However, if you have a flame impinging at the upper part of the tank, it will create enormous pressure while weakening the tank. When the upper tank ruptures at the point of impingement, you have a massive fireball the size of a city block. Note it blows out at the site of impingement-it doesn't blow out the ends every time. In fact, the ends are much stronger than the top of the cylinder. Now, when LP gas boils at -44F, it expands 277 times so you get an impressive little fireball.

If this theory about the ends of LP tanks being so dangerous then why don't they make bobtail delivery trucks with cylinders pointed to the sky and roadway? Does this mean you are in danger of following right behind these trucks? This is silly. Sorry,

Originally Posted by Ken Amelin

From a physics stand point ..... If the tank was completely without safety features and the pressure was such that the tank would rupture, by design and shape of this vessel, it would rupture along the seam of the cylinder -- NOT the end caps.

Thanks, Bob and Ken, I'm posting a couple of BLEVE links here. I imagine the theory is that the welded seams would let go first, but as you say, most likely it would be the valves blowing out first and the rupture starting there.


YouTube - BLEVE (Boiling Liquid Expanding Vapor Explosion) Demonstration - How it Happens Training Video

YouTube - Mexico BLEVE Explosion

I took this pic a few years back, practicing with my paint pole cam. This tank was not pointing at my house. It was pointing at the power pole to the left and my neighbor's house on the right. Glad I got rid of it.

per NFPA 58 if that tank is 500 gallon wc or left it can be 10 feet from the house and / or property line. The point of transfer requirement is also 10 feet from any source of ignition. As a rule in the 30+ years I have worked in the gas industry both LP and Natural we didn't point the bullet end at a structure. Vehicles are more of a threat but the closer the tank is to the house the greater the risk.

Jack M