Let’s face it, we are all curious about what the inside of your RV propane tank looks like. (Insert sarcastic look/comment here). Well, have no fear, if you have ever wondered about the various parts and how they work, the mystery is about to be revealed.
For expert advice, we turn to long time RVer Campskunk, from the website Roadtreking.com.
Let’s start with the familiar and go from there. First we will take a look at the gadgets and their corresponding fittings that are located on the outside of the tank. From right to left we have the tank main valve, the bleed, the fill port, the relief valve, and the fuel level gauge.
Because we’re not all technically minded, Roadskunk thoughtfully breaks down the technical aspects for us so we can understand the role that each part plays. Here it is in a nut shell. Approximately 80% of the tank is filled with liquid propane, the rest is made up of propane vapor. Believe it or not, the vapor is what your RV system runs on. If liquid propane gets into your RV plumbing, it will damage your pressure regulators. The idea is to fill the tank up to 80% and use the vapor from the top. Okay? Okay, let’s talk specicifcs.
The Fill Port
The first part that we are going to talk about is the fill port. All the fill ports installed in the past decade have an overfill protection device or OPD. The OPD has an object that looks like a yellow hot dog (called a float) that sits on the edge of the valve. It is attached to a moveable arm. When the level of the liquid propane rises in the filling tank, the float will rise up and move the arm. When it has reached the right level, the arm will close the valve. This valve pinches the hole that the propane enters through.
As Roadskunk reminds us, this is how it’s SUPPOSED to work. If the float is broken, or the arm is bent or was installed wrong, it won’t be able to perform its job.
To be honest, the protection in the name of this device covers the propane fillings station. Its job is to make sure that your tank doesn’t blow up on their property. In other words, it’s not designed to protect your RV propane devices or give you an exact 80% fill every time.
Next up is the bleed, which is the device located to the immediate right of the OPD float.
The bleed is a vent connected to a pipe inside the tank. This pipe goes up to the height that denotes that your tank is 80% filled. It opens inside the tank, and if the tank is below the 80% mark, the end of the pipe will be in the propane vapor. If the level is at or above 80%, a white mist of liquid propane will come out. The bleed doesn’t have any moving parts. It is foolproof and makes sure that your tank doesn’t get too full.
Roadskunk advises us make sure the bleed is used when the tanks are filled.
If a fueling technician refuses to use the bleed to fill your tank and just relies on the OPD, immediately stop him and find another place to buy propane. He isn’t going to buy you new regulators.
If for some reason you tank gets overfilled, leave the main valve shut. Go to a nearby remote location and turn off all ignition sources in your RV. Your next step is to park with the tank on the side of your rig that is downwind. Now, you must vent the liquid propane until the only thing that’s coming out is vapor. Then, and only then, can you open your valve and begin using your propane. If you are unsure that you will be able to do this, go to a propane shop and ask a technician for some help.
The Fuel Level Gauge
The fuel level gauge looks like a little black paint roller. It’s located on the far left of the tank. It works much in the same way as the OPD float, i.e. the float rises and lifts the arm along with it. This arm moves a magnet and a gauge on the outside of your tank senses its position. This will generate a reading for the gauge on your tank as well as the one inside your RV. This magnet setup makes sure that your tank doesn’t have any electrical connections. But, this doesn’t mean that the reading is accurate.
The Relief Valve
The relief valve is located to the right of the fuel level gauge. As the name suggests, it’s a valve that connects to a big pipe that goes into area where the vapor is. It’s only job is to prevent your tank from exploding if overheating occurs. If you’ve ever seen the big plume of flame that comes from the bottom of burning RVs, then you’ve seen this in action.
Most RV fires are either electrical, or the result of campers playing with fire. If you ever notice that your relief valve has opened up, make sure that you turn off all the sources of ignition. Also, you will want to immediately leave the area until it stops venting. If propane has already been ignite, skip the first step and run as if your life depends on it because it probably does.
There is a pipe that is connected to the main tank valve that is like the relief valve. The only difference is that it is bent instead of straight. It is big and goes all the way up to the area where the vapor is. You can open this valve by slowly turning it counterclockwise. It must be done properly or its safety device, called the slam-shut valve, will think that shut it down. To reset this, close the valve, wait for about five minutes, and try to open it again… slowly. You can close the valve by turning it clockwise. If you are going to refuel or smell a propane leak, turn off your battery disconnect switch. Also, you will want to turn the valve off to drive your rig.
We’re done. See how simple that was? As you can see, if you follow the rules, propane is as a safe as any other type of fuel. Happy Traveling!