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Ask Dave: Why does my RV propane regulator whistle for only one tank?

Dear Dave,
Why does my RV propane regulator whine or whistle when it’s pointed to one tank but not to the other one? —Dennis

Dear Dennis,
The propane regulator of your RV reduces pressure to 11 inches of water column and has a rubber bladder that can create a humming noise, but a whistle or whine is an issue. However, since it only does it on one cylinder, we need to look at what might be wrong with that tank. From your description of “pointed to one tank but not the other one,” it appears you have either a travel trailer or 5th wheel and your LP container would be classified as a DOT cylinder.

I do have some questions:

  • First, when did the whistling start? Was the unit new when you purchased it and it started from the first fill?
  • Did it work OK for you in the past, either new or used and just started?
  • Did it start after a new fill or new cylinder?
  • What is the date stamp of your cylinders? Is the one that whistles older than the other?
  • Have you filled the cylinder since and it continues?
  • Have you switched positions of the cylinders on the tongue platform?
  • Does outside temperature make a difference?
  • Does the whistling occur all the time or at a certain level of LP in the tank?

Answers to these questions can help pinpoint the issue.

LP leak detection

The first thing I would do is check for a leak with a portable propane leak detector that you can get on Amazon.

Overfilled propane cylinder?

It’s hard to believe in today’s age of over-protective devices and safety measures that a propane container can be overfilled; however, it does happen. An overfilled cylinder can cause a whistle and even worse. Check out this article posted in RV Travel from 2020.

If you have refilled the cylinder since this started and it still whistles, then it is probably not an overfill situation… unless the same guy filled it. I’ve learned never to say never in the RV industry! Here is where I would suggest swapping out the cylinders to isolate a cylinder issue. If you swap the cylinders and the whistle follows that cylinder you have found what we call the “common denominator.” If it switches to the other cylinder, it is a POL (originally for Prest-O-Lite) valve that is the connection.

Moisture in the cylinder

If the cylinder is not purged properly when new, there could be moisture in the cylinder that would cause an issue with the rubber bladder in the regulator. Here is the proper procedure to purge a new cylinder according to NFPA 58:

  • Exhaust to atmosphere any air pressure in the container
  • Pressurize the cylinder to 15 psig with propane vapor.  Never use liquid propane.
  • Exhaust vapor to atmosphere
  • Repeat four more times

Several years ago I helped develop the RV Safety & Education Foundation’s Safety Program, and we did extensive research on the Propane Safety segment. I worked with the NFPA, Propane Safety Council, and several Original Equipment Manufacturers (OEM) such as Manchester Tank and Marshall Brass. They had the following recommendation:

“In order for equipment to operate safely, both new cylinders that have not been vacuum purged by the manufacturer and those that have been opened to the atmosphere must be purged of air or moisture before they are filled. If air or moisture enter a propane cylinder, they can slow down the filling operation, create unusually high service pressures, may cause regulator freeze-up, and may cause fading of the odorant in the cylinder. Purging should be done in an approved area as outlined in NFPA 58, usually at a propane plant, and is never done with propane liquid.”

Temperature

If the outside temperature gets down in the 40s or lower and the cylinder is getting low, it can cause this issue. I am not as familiar with the dynamics of this, but it’s a good time to see if switching tanks around makes a difference. The more you can identify the operation, the easier it is to isolate the issue. It might be that you are using cylinder 1 the majority of the time and only switch to cylinder 2 when 1 is empty, and then switch back when 1 is filled. Again, the reason for swapping the cylinders out when they are both full to see if there is a difference.

POL or connection

The hose and connection to your DOT cylinder is commonly a POL-type connection and is not often an issue with the situation you have. However, swapping the tank is a good way to determine if the whistle sound follows the tank. Or the position will tell you if it is in the POL connection or hose. If it follows the connection, I would replace the entire POL and line.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

Read more from Dave here

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JAMES
6 months ago

Cause one tank is prettier than the other tank.

Mike
5 months ago
Reply to  JAMES

Lol

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