Using the old-style POL (left-hand thread) propane fittings on the newer-style OPD tank fittings will eventually distort the gasket inside the OPD. When you subsequently hook that tank up to a newer ACME-thread (hand-tighten) fitting, it will likely leak propane.

The gasket inside the OPD valve is somewhat difficult to remove, and is supposedly not replaceable, requiring replacement of the entire OPD valve on the tank. If it's a 20-pound tank, no biggie, just go exchange the tank.

However, that's not so easily done when they are 30-pound tanks, especially if they are full or nearly-so.

What I am about to say is for informational purposes ONLY, and I am making NO recommendations.

It is possible to pull out the rubber gasket with a small pair of needle-nose pliers.

The rubber that is pulled out is very, very similar to a Brasscraft #SCB0094, which is a Buna-N (nitrile) bonnet packing washer for a Kohler faucet, available on-line.

I believe that's all I wish to say....

Pop

 

good tip to try to save the bottle till it is due for recert at least.