Sunday, January 29, 2023


Ask Dave: Why can’t anyone fill my RV’s LP tank?!

Dear Dave,
We’re having trouble filling our LP tank. We put LP gas into the tank twice. Then four individuals at the local supplier were unable to put LP gas in the tank, so one individual put LP gas in the tank through the exit line. I assumed a new input valve was needed so I had one installed, but it turns out there was nothing wrong with the old valve. I took the RV to a local supplier and another two employees were unable to fill the tank. Then I took the RV to a second supplier and the employee was initially unable to put LP in the tank. He wiggled the hose and was then able to put it in. Why have so many people been unable to put LP in the tank? What is happening? Thanks for your help. —Gordon, 2021 Thor Gemini

Dear Gordon,
Your 2021 Thor Gemini has a permanently mounted ASME (American Society of Mechanical Engineers) tank, which is a horizontal mount in an unlocked compartment on the driver’s side of the rig. Manchester Tank is the Original Equipment Manufacturer (OEM) and typically they use a Marshall Brass Overfill Protection Device (OPD) at the fill valve.

This is the yellow-capped valve in the photo. It concerns me that someone filled the tank “through the exit line”! When it comes to propane, I have the utmost respect for it and the system. I always defer owners to a certified technician as I have seen too many issues, some resulting in fires.

When you described the attendant “wiggling the hose” and it worked, I assume you are referring to the LP station supply hose as there are typically no hoses on your tank.

As you can see from this diagram, everything is fixed and the device coming off the vapor service valve goes directly to the LP regulator.

Issues with places filling RV LP tanks

An issue I see in the LP service industry is that many places, like fueling stations and even hardware stores, are putting in LP fueling stations with a large bulk tank. From there, employees are given a very brief “certification” course, which only covers minor filling procedures and safety procedures. These employees are not trained in the mechanical components of the ASME tank and service operations. (Read about Randall Brink’s experience with this here. Yikes.)

I am not sure what “input valve” you replaced, but the only thing that should be installed is an Overfill Protection Device such as this one.

The valve to fill an LP tank

This one is used in a DOT cylinder used in trailers. The one for your tank has 80% float to limit overfilling. The on/off handle is to the side, as shown in the first photo. This is not something that the average RV DIYer should attempt, but rather a certified LP technician.

I would suggest contacting a certified technician to have your system and valve inspected as there is definitely something not right if so many attempts were made unsuccessfully to fill the tank.

 You might also enjoy this

Two options to refill propane; one is a rip-off

B Gail Marsh
It’s cold! And before long, winter’s temps will be even colder. For RVers who love to travel in the cold and snow, propane is a necessity. In warmer temps, you mainly use propane to fuel your grill and perhaps the RV’s oven/cooktop. However, in colder temps, you need propane to stay warm and comfortable. In some cases, you may need it to stay alive! The cost of propane that fuels your RV furnace has increased significantly in the past several months. That’s why it’s important to know about the propane refill rip-off. You need to know the difference between paying a flat rate for propane or paying only for the propane drawn. Continue reading.

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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Jesse Crouse
1 month ago

Under NO circumstances should an untrained or non industry certified person be filling or altering a propane installation. This from a Master Plumber with 55 years in the plumbing and heating industry.

Bob M
2 months ago

Why don’t they put 20# or 30# portable propane tanks like grills use on motorhomes. Seems like a pain getting propane in motorhome tanks.

2 months ago
Reply to  Bob M

I have a 30 gal ASME tank on my coach. 80% is 24 Gal x 4.2lbs = 100.8 pounds. That is a lot more propane than you can fit in 2×7 gal tanks. Also ASME tanks are not subject to expiring like portable cylinders. Actually it is much more convenient. Many campgrounds can fill as well as Flying J and other outlets if you keep your eyes open. It is always fill by gallon. The 80% fill limit also provides headroom for vapor which is needed because we use the vapor not the liquid for distribution to appliances.

Jesse Crouse
1 month ago
Reply to  Bob M

A bigger pain is the “KABOOM”. Just ask Wiley Coyote!

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