Airstream Central - Info for Airstream Owners -
Overfill Protection Device (OPD)
Dan Brown
I have been working at the Out-of-Doors Mart (The Longest Running Airstream Dealership in the World) for over 10 years. I handle the on-line sales and Web development. 
By Dan Brown
Published on 04/12/2008
This Article is about the Overfill Protection Device (OPD) that is on the new PL gas tanks that are on RV's. It is intended for the new Airstreamer who has aluminum LP Gas Bottles/tanks and can't get them filled because they have the old valves on them.

Overfill Protection Device (OPD) What,Why, and How to upgrade
OPD stands for Overfill Protection Device and is a device that keeps the LP Gas bottles from being overfilled. If LP gets hot, like in the summer when it hits 90 degrees, it wants to expand. When LP Gas expands it becomes unstable and wants to explode.  This new device prevents this from happening by cutting the valve off and stopping the bottle from being filled to over 80 to 90 %.

When the bottle becomes full the float moves upward and stops the gas from coming in.
If you have the Aluminum LP Gas Bottles/tanks (seen below) you most likely won't want to discard them, just because they have the old valves.

There is a difference between the steel and aluminum tanks. The difference in respect to the OPD is the shape of the tank. The aluminum tanks are taller and the OPD that is designed for the steel tanks does not work properly in the aluminum tanks. Aluminum tanks are substantially lighter as well.

All tanks, steel or aluminum, have to be pressure tested every 12 years if they are new and every 5 years if the valves have been replaced. So if you have steel tanks it is not cost effective to replace the valves not to menchion the hassle of having the valves removed, and the tanks pressured tested  every 5 years.

If you have steel tanks, the gas companies that sell the gas will take the tanks at no charge. When the bottles are empty just drop them off. The Out-of-Doors Mart and many other retailers sell the steel tanks ( 30 lbs   and 40lbs  ) but if you do not live with-in driving distance, your better off getting them from a locally to where you live.

If you have aluminum tanks and want to keep them ( I sure would) then you need to replace the valves.  The valves need to be replaced. The companies that do pressure testing have the tool to remove the valves and put the new ones in. The problem is, most of them do not carry the aluminum OPD.

The other great benefit of the OPD that you hear little about from a safety stand point is shut off feature. If the gas valve is just opened up the gas will NOT come out. The good thing about that is, if you were to have an accident,( no one likes to think about that, but they do happen) and you sever a gas line the gas is shut off, unlike the old valves.

Another great benefit of the OPD from a convenience stand point is the way you can attach the hose. The new valves support a  "hand tighten" attachment, verses the old "brass and wrench". If you have ever had the old style you know what I'm talking about.

I hope this helps shead a little light on the subject if you are new to Airstreams.
As always comments and questions are welcome.

Dan Brown