How to Convert Propane Tank Fittings

by Nathan Fisher

Because gas expands as air temperature rises, to avoid the risk of explosion propane tanks must only be filled to 80 percent of capacity. As of April 1, 2002, federal law mandates all portable vertical propane tanks of 4- to 40-pound capacity be equipped with a new “quick-closing coupler” overflow protection valve or adapter. The new QCC-style valve replaces or adapts the older style “Prest-O-Lite” valves to ensure propane tanks are not accidentally overfilled.


Disconnect the propane regulator from the propane tank with a wrench. Clean the threads on the insides of the existing female Prest-O-Lite fitting with a piece of fine-grade steel wool and wipe the threads clean with a cloth.


Insert the male end of a quick-closing coupler adapter into the neck of the existing POL fitting on the propane tank. Twist the QCC fitting tightly in place with your hand.


Place a spanner wrench over the flange on the quick-closing coupler. Turn the spanner wrench counterclockwise until you hear the nut inside the adapter “snap,” signaling the adapter has permanently locked in place on the POL valve.

Items you will need

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