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Standards Division

LP Gas Concerns > Cylinder Valves

Richard Fredenburg, LP-Gas Engineer


Drawing of a propane grill cylinder

If you cook using a gas grill fueled by propane, you may have noticed a change in how the valve on the propane tank looks. Also, if you bought a gas grill in the last couple of years, the tank that came with the grill and the connection on the grill probably look different from what you are accustomed to seeing.

First, a description of the basics of how things were and what has changed. Then, how it may affect you when you need to get more fuel.


POL Valves

Drawing of a POL valveThe old-style tank valve is known as a POL valve, named for the manufacturer that devised it. You tighten the connection to the grill by turning the fitting counter-clockwise, and you usually need to use a wrench to make the connection tight enough to prevent leaks. With a POL valve, if you open it with no fitting attached, propane is freely released. That's why a plug is required to be screwed into the valve during transport of the tank and when it is stored not connected to the grill. The plug is an attempt to keep little hands from opening the valve and creating a danger for themselves and others in the area. This valve also has a built-in bleeder valve for the refiller technician to use to check for proper filling and a pressure relief device to prevent overpressurization of the tank.

A safety note for you: Propane tanks of any design must be transported and stored in an upright position so the pressure relief device will function properly. Laying the tank on its side in the trunk of your car is a potentially very dangerous situation.

Acme Valves

Drawing of an Acme valveWhat has changed? There are actually two pieces of equipment that changed. The most obvious is the valve on the propane tank. It looks bulkier because there are external threads visible. This valve is known as an Acme valve, for the Acme threads visible on the valve. It also has a slightly larger body, for reasons to be explained later. The other piece of equipment that changed is the connector on the end of the grill hose. If you bought a new grill in the last couple of years, you have probably already noticed that the fitting on the grill is also larger and that you can now attach the hose to the tank without having to use a wrench. One of the benefits is that the connector is designed to be attached to the tank without tools. You only have to hand-tighten the connector. And, you tighten as you would normally tighten a threaded fitting, by turning it to the right (clock-wise). The gas-using device (grill) must be securely attached before a built-in safety device opens and allows the gas to flow freely.

What happens if you have an older grill and have to replace the tank and get one with the Acme valve? Use it. They are compatible, as the left-hand-thread fitting on your older grill will screw into the internal threads on the Acme valve.

Also, there is another type of valve not widely available yet. This one is a quick disconnect, somewhat like a fitting that attaches an air hose to a pneumatic tool. This fitting will be covered later in this article.

OPD Valves

There is a new type of valve quickly comming into use. This valve is the Overfill Prevention Device (OPD) valve. It looks a lot like the Acme thread valve or the quick disconnect valves you have been seeing for a few years. The OPD valve has another safety feature inside the container to prevent overfilling the cylinder. You can tell the if you have an OPD valve by looking at the handwheel. The OPD valve has a distinctively-shaped handwheel. It has three lobes instead of the five or more on older valves.

All new cylinders from 4 pounds up to 40 pounds propane capacity must have the OPD valve. All cylinders from 4 pounds up to 40 pounds will have to have an OPD valve by April 1, 2002, or it will be illegal to fill them. It will not be illegal to use or transport them, only to fill them.

You can find cylinders with the new OPD valves at many places, including propane companies, hardware stores, and discount stores.

Please click here for information concerning disposal of old or non-OPD-equipped cylinders.


When You Get Your Tank Filled

Now that you know how to make the connection between the grill and the tank, you need to know what the difference is in getting your tank refilled. If you take it to a place that fills your tank, you will notice no difference in filling the tank. The same piece of equipment that fills tanks with the POL valve will also fill through the Acme valves or OPD valves because of those internal threads. But there is a difference you need to recognize after you get your tank filled. As you get ready to travel with your newly-filled tank, instead of screwing a plug into the internal threads, you may press the optional dust cap over the external threads. The Acme valves and OPD valves have some built-in safeguards that prevent the escape of gas when the tank is not attached to the grill, even if the valve is open. This is the reason for the valve body being slightly larger. However, if you screw a plug into the valve, you defeat these safeguards. So be sure to leave the plug out of the Acme valves and OPD valves!

Safeguards In the New Valves

There are some other safeguards in the valve and connector combination that stop the gas flow if the tank is involved in a fire, even if the tank is still attached to the grill and even if the valve is wide open. Another safeguard limits the flow of gas from the tank should the hose break or leak.

What To Do If The Grill Won't Light

The safety devices require you to open the valve on the tank before you open the burner valve. Otherwise, all you will get is enough gas to run a pilot light. If your grill will not light, try this:

  1. Close the burner valve, leaving the tank valve open.
  2. Wait a few minutes. (You may have to wait longer if you have a long hose.)
  3. Go through the lighting procedure again, opening the burner valve according to your grill's instructions.


When You Exchange Your Tank

You need to be attentive if you go to a cylinder exchange cabinet to turn in your empty tank for a filled one. If you have the old-style connector on your grill, you can use both of the widely-available screw-on valves. However, if you have a new grill with the connector that needs the new external threads, be sure to get a tank with the new Acme valve. Some of the exchange cabinets offer many tank styles. Get the one you need. Remember, the Acme valve will work on both styles of grill connectors discussed so far.

You may still see some non-OPD-equipped cylinders after April 1, 2002. This is legal. As mentioned earlier, you may use and transport non-OPD cylinders after this date. But you cannot have them filled.


Quick-Disconnect Valve

As mentioned earlier, there is also a quick-disconnect valve and fitting combination available. (Some Weber gas grills use this fitting.) To make the connection with this combination, you simply pull back slightly on the collar ring on the valve and press the fitting firmly into the hole in the valve until it "clicks" into place. It will remain in place until you slide back the collar on the end of the valve. This valve and connector combination also has the safeguards mentioned earlier for the Acme valve. Your refueling choices are more restricted with this combination. These are rarely stocked in exchange cabinets. When you bought the tank with the quick-disconnect valve, you probably received a special fitting to be used to fill the tank. The fitting has the internal POL threads that allows the refiller to attach his equipment to your tank. Your refiller may or may not have this fitting. Be sure you have the fitting with you when you go to the refiller and when you leave with your full tank.


Safety Tips

Propane tanks make grilling easy and convenient. In most cases, grilling is a pleasant way to spend a summer evening or weekend outdoors with family and friends. There have been few problems with propane tanks in these situations, but the potential for problems exists, as it does with any source of energy. To reduce the possibility of these problems, follow these steps:

  1. Keep spare propane tanks away from the heat of the grill.
  2. Use and store propane tanks outdoors only and in an upright position so the valve is at the uppermost part of the tank.
  3. Never carry tanks into a house or other type of building.
  4. If the tank becomes corroded or looses its collar ring (the carrying handle) or its foot ring (the support ring on the bottom), replace the tank immediately.
  5. Do not allow young children to play with the tanks, especially the older-style, POL valve equipped tanks.

With these simple precautions, you can continue to count on your propane grill to provide a safe and convenient way to grill.


Who to Contact

If you have questions about propane containers or propane use, contact your propane dealer or Richard Fredenburg, LP-Gas Engineer with the Standards Division, North Carolina Department of Agriculture and Consumer Services. Our address is 1050 Mail Service Center, Raleigh, NC 27699-1050. Our telephone number is (919) 733-3313.

Last updated August 11, 2004



NCDA&CS Standards Division, Stephen Benjamin, Director
Mailing Address:1050 Mail Service Center Raleigh, NC 27699-1050
Physical Address: 2 West Edenton Street, Raleigh, NC 27601
Phone: (919) 707-3225; FAX: (919) 715-0524