Propoane Tank Issues

Disclaimer up front- I'm not an engineer, nor do I have any other credentials pertaining to this- but, here's some information that you may find comforting:

A typical residential hot water heating system operates at water pressures between 12 and mid-20s PSI (pounds per square inch); that's less than the pressure found in a typical car tire.

Propane, on the other hand, when compressed to the liquid form in which it can be stored in volume in a tank, has a pressure that's vastly higher- the exact figure isn't anything that I remember or can find easily, but I believe it's well over 100 PSI-and I think actually well higher than that.

In a properly designed, installed, and operated hydronic heating system, air/ oxygen should be purged and subsequently remain out of the water within the system, such that there should not be significant corrosion.

From what I've seen of propane tanks that have been cut open, the walls are in the vicinity of 3/16 thick steel -- other than corrosion, how could that leak/fail in a short period of time in this intended application?

They are pressure tested to over #350 psi. They are 1/4 to 3/8 thick. I have one that is being used for propane that was certified in 1975 and as long as I keep it painted it will be good for ever as long as the data plate can be read. The ones that I got for my water storage and that I sold were ones that the propane co took out of commision and they were all in good shape buy were removed because the paint was chipped and they were getting small rust spots or the port location was different than what they were using. It was cheaper for them to buy new than to send them out and have them repowder coat them. Plus they want to have nice white ones for there customers. Unless yours is DEEPLY (like 1/8in or more) pitted you don't have any worries and even then it shouldn't be a problem.
leaddog

Look at the outside / bottom and that's where you'll find the rust, it's actually more pitting, as leaddog said. I don't believe the insides rust much. After washing my tanks, I sanded and spray painted exteriors.
If your tank started to leak it wouldn't be like a rupture and you'd have 500G of water on the floor in a couple of minutes. I believe it would start as a pinhole. Identify the leak and have a welder fix it would be the worst scenario.
That said, 500G of boiler water is NO joke and needs to be treated with respect. Such as, having your supply and return pipes properly supported. I fitted my drain on the bottom of tank with a 2nd cap so if the valve gets opened by accident ( handle is removed also ) no water will come out.
Go for it. I'm heating storage while writing this and will have hot water till Wednesday !
Rob

My propane tank which is owned by the LP gas company was manufactured in 1971 and is still going strong. They have painted it once or twice since installation in the fall of 1997. I travel all over Michigan for work and have noticed most propane companies have tons of old tanks laying around in their yards. Seems like they would be willing to part with some of them if anyone needs one. I've also seen trucks hauling old tanks north on 131 from out of state. Not sure why! Plate on my tank also states 250 psi at 650 degrees fahrenheit, shell thickness 0.293. It also states... do not fill with a product that will exceed 215 PSI vapor pressure at 100 degrees fahrenheit. Manufactured by Chemi-trol, chemical company ????mont, Ohio USA.

I've seen a couple of instances where propane tanks leaked, however it was at the fittings not through the shell. Unless the tank is seriously pitted I can't believe there is any way it will be the first thing to rust out in your system.