Dear Dave,
Is there a “back seat” on propane valves on our tanks, like the valve on an oxygen cylinder? Should the valve be opened ALL the way, or just enough to provide enough gas to flow for your needs? —Stormy, 2014 Forest River Wildwood
Dear Stormy,
I was not familiar with the term “back seat” so I did some research and it seems it is a common function of oxygen tanks that are used for welding and medical purposes. It seems they have two valves, one that seals when closed and a second seat on the valve that seals when the valve is fully open. Oxygen tanks are high pressure and require the two valves. According to my tech contact at Manchester Tank, propane is relatively low pressure in comparison and does not need a second valve.
DOT cylinders
Travel trailers and 5th wheels have DOT cylinders that can be 20 lbs., 40 lbs. and even larger. As of 1996, all DOT cylinders were required to have an Overfill Protection Device (OPD) type valve that would only allow the cylinder to be filled to 80% to allow expansion of the LP vapor.
The OPD valve must have a triangle handle for a filling location to legally fill the cylinder.
For years, POL fittings and pigtails were used. POL stands for Prest-O-Lite, the company that designed them. Today, DOT cylinders use a Type 1 or ACME fitting like the green connection on this cylinder. These have a spring-loaded excess flow valve incorporated and thermal protection.
It is recommended to initially open the triangle valve slowly. Otherwise, the burst of LP pressure will push the excess flow valve and shut off the supply of LP for several minutes until the back pressure in the system allows it to open.
Then it is recommended to open the valve all the way, as the LP regulator is designed to regulate the proper pressure needed. Smaller units with few LP appliances typically have a single stage regulator.
You might also enjoy this from Dave
The ultimate guide to liquid propane (LP) systems
This is Part 7 of Dave Solberg’s “Everything you need to know about RVing” series. In this installment, Dave looks at RV liquid propane (LP) and explains what you need to know about it including how to be safe using it. This is useful information whether you’re heading out on your first or 101st RV trip.
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
Read more from Dave here.
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And before lighting the water heater, furnace or fridge when on propane, turn on a burner on the stove until it lights.
This will insure the lines are bled.
You left us hanging. Go on to explain why the need for a 2 stage regulator vs a single stage regulator. I’ve had both in my rv equipment & never understood the difference.
Thank you, Dave! 🙂 Have a great day! 🙂