Tuesday, September 26, 2023


Understanding your propane regulator

By Russ and Tiña De Maris
Unless your RV is a motorhome, chances are good it has an automatic changeover regulator. We say that, as motorhomes come equipped with a single propane tank and all others commonly have two removable LP cylinders. We’ll use the terms “LP” and “propane” interchangeably.

Having two removable containers is really a blessing. If one goes “dry,” it’s a quick and easy step to take the empty out for a refill, leaving the other container with the rig, keeping stuff like the refrigerator operating. No need to move the RV to refuel the propane.

What makes this setup work so well is an automatic changeover regulator. The LP regulator reduces the pressure of the propane stored in the tank to a level your appliances can safely use. An automatic changeover regulator allows you to disconnect either one of the LP containers while keeping the other propane container “on line.” And it does so automatically, so if one goes empty the other simply steps in and takes over the job without you having to get involved.

An automatic changeover regulator has a sight glass, which indicates whether the container has fuel in it or is empty, and a way of directing the flow of LP, be it a knob or lever. Here’s how it works:

R & T De Maris photo

When you have your LP containers filled, and are in camp, open the valves on both LP bottles. Regardless of which way the knob or lever points, the sight glass will indicate a cylinder with LP in it. Mind you, the flag only indicates if there’s fuel present, not how much. In the case of the lever-type regulator shown, the lever points to the tank being checked — in this case, the left tank. Once the left tank empties out, the regulator will automatically begin to draw from the right tank.

The regulator pictured shows the left-hand tank is being checked. Notice that the sight glass shows green (the little green line just below the black cap at the top) – the left cylinder has fuel in it. Once this cylinder is empty, the sight glass flag will change to red. If there’s fuel in the right cylinder, the regulator will automatically switch over to draw LP from it. Some older regulators may use a silver-colored flag to indicate gas, with a red flag indicating empty.

How do you change out an empty bottle? Once the flag in the sight glass shows you have an empty, TURN the lever (or the pointer knob) of the regulator toward the “full” bottle. Then TURN OFF the empty container supply valve, and you can then safely remove the empty container by disconnecting the rubber “pigtail” or connector hose. If you don’t FIRST change the regulator pointer, when you disconnect the empty cylinder, you may find LP rushing out of the pigtail.

When you bring the refilled cylinder back, slip it into place, connect up the pigtail, and open the supply valve. Just leave the lever or pointer on the regulator pointed at the other cylinder – it will “flag you” when it’s empty.

These automatic changeover regulators are not only useful in keeping you in gas, they can also tell you if there’s a leak in your RV propane system. Here’s how to tell:

With all propane appliances in the RV turned off and no pilot lights left lit (or turned on), turn off the gas valves on your propane containers. At this point, the regulator sight glass flag should show “full.” If within a few minutes (or even a few hours) the sight glass flag shows “empty,” it’s a safe bet there’s an LP leak somewhere in your system. Get your system checked.


Russ and Tiña De Maris
Russ and Tiña De Maris
Russ and Tiña went from childhood tent camping to RVing in the 1980s when the ground got too hard. They've been tutored in the ways of RVing (and RV repair) by a series of rigs, from truck campers, to a fifth-wheel, and several travel trailers. In addition to writing scores of articles on RVing topics, they've also taught college classes for folks new to RVing. They authored the book, RV Boondocking Basics.


  1. One downside of using the auto change over feature is that you can empty both propane cylinders completely before you notice you have no gas supply. I keep the full cylinder shut off until the cylinder in use is close to empty. It helps me keep track of my propane supply and avoids running it empty. In rural areas propane fill stations are frequently closed on weekends so if you run dry you may be out of propane for two days.

  2. Thanks for great information. It make me more understand about my rv so I can understand and choose a fittable propane for me.

  3. actually a regulator does more than reducing pressure from tank pressure to line pressure – it also maintains that pressure regardless of downstream demand. for example whether one range burner is being used, or three range burners, water heater and furnace at the same time the regulator maintains the same line pressure on the system.

  4. i don’t see a green line…maybe tomorrow after I get my cataract surgery I will! What if you have one that lets you put the switch in the middle? I thought mine was drawing from the one turned to and did the switch over when in the middle.

  5. Great explanation for those who didn’t understand how the regulator works. That was me when I was new to RV’ing.


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