Replacement Seals/O-rings for Portable Propane Cylinders?

My valves have both external and internal threads. One of these with it’s own O ring might solve your problem.

Amazon

when mine started to crack and leak i took it to the propane dealer and they said no way to change out just the o-ring i that to get a new valve installed

Though the seal ring was on the adapter not the cyliner.. but as others have said any propane wholeseller, Most RV stores and hardwares.. A "Fireplace and grill store" all should have it.

Do you have a brand and model number for the valve?

Worse come to worse they can just replace the valve, I've had it done on a couple of tanks. Last time they didn't even charge me since I filled up several tanks. I actually think that the maintenance guy didn't write up a ticket and the women up front said 'to heck with it"...heh.

This one?

https://www.jmesales.com/1-3-4-in-lp-gas-acme-gasket-

Thanks, Agesilaus. Like you say, I don't want to cobble this up since the risk is high. But yes, I am a big fan of the true "hardware stores" where you can buy just about any kind of oddball part you might need. Any RVer should be familiar with their closest hardware store (NOT the same as Lowes or Home Depot).

Call a local propane/gas business and find out which of the local shops does tank maintenance. Take it by there.

As an aside if you go to an Ace hardware store they will have a, what I call, a wall of parts. Row after row of cardboard drawers. Some Aces have bigger walls than other. And in some of those cardboard drawers you will find o-rings and gaskets. I don't recommend doing that for the propane tank since it's a safety issue. But next time you are in an Ace just take a look at the wall to see the wide variety of stuff they have. Sooner or later you will want a knob or spacer or who knows what else.