RV Propane Line Cap: How to Cap an Unused Propane Line

Sometimes simple alterations to your RV or trailer can create bigger hassles. When you remove a fridge and do not replace it with another one, you need to do something with the propane line. That can be a big hassle if you are not careful.

This is not hard to do and sometimes a simple cap bought at a big box store will handle the job. The key will be to use two wrenches when tightening the cap and then testing the seal with soapy water. You always need to test your work to make sure it is safe.

To learn more about capping a propane line, just continue to read our article. It has the information you want to know about so that your alterations do not lead to bigger hassles or bigger problems. Keeping it simple is always the best fix.

Can You Cap a Propane Line?


Yes, you can cap an RV propane line. The type of cap you use will depend on the type of fitting the line has. For a flared end, you would need a flared cap as the seal is at the surface, not the threads.

Some people caution that you should not cap the propane line inside your RV. Instead, you should trace the line back ways and cap it at the T fitting where the line heads to the fridge or other propane using appliance.

Keeping yourself and your family safe is the first priority when doing work like this. You want to make sure the cap is designed for the fitting used on line. That will give you the best seal.

Then usually, you do not want to use tape, any kind of tape to cap off the line. Always opt for the proper equipment and supplies to handle the task. Then test your work to make sure there are no leaks.

How To Cap an Unused Propane Line

If the propane lines are not going to be attached to anything, then the best solution would be to install shut-off valves. These can be installed in different places along the propane line or lines. That is if you do not already have propane shut-off valves installed.

If the lines are unhooked already, place a child’s balloon, uninflated, over the end of the line or lines. Then if the balloons inflate, you need to buy the proper cap for them. If they don’t then the gas is shut off already at another location and you should be able to simply tape the ends securely. Duct tape is always good in this situation.

If the balloons do inflate, that means you need to go to the hardware or home improvement store and pick up the right cap. If you can’t take the end with you, take a photo of it and bring the photo with you That will help you get the right cap.

Then just use a wrench on the fitting side and a wrench on the cap side to make sure you get a tight seal. That is all there is to it. if you have a spring-type valve, on your propane line, they may be illegal in some states. You would need to replace that valve and then cap the new one.

RV Propane Line Cap


There are many different types of propane line caps for RVs. Some come with fittings that go in different directions and all they are made of are plastic materials. They just slip into the opening and the line should be sealed.

Then there are threaded cap plugs that should fit in most propane line fittings. They screw in without help from tools until the end. But do not try to over-tighten these caps as they may crack on you.

Purchasing the caps is not going to be that hard. Most hardware, big box stores, and RV parts and supplies stores carry a fair number of them. You will have to measure your fitting to make sure you get the right diameter of the cap.

If you do not need your propane tank, you can buy a plastic cap to stop the propane at the source. This is often your best choice as to if there are any leaks, the gas just stays outside of your trailer, etc.

The major problem you will have in capping your propane lines will be the location of the lines, the position of the fittings, and your stature. In some cases, your body may be too stout and arms too short to reach the lines or fittings to cap them properly.

Can The Gas Line Be Capped For a Propane Stove?

Yes, it can and the above information will guide you to doing the job right. Usually, people cap the lines when they are removing the stove for whatever reason they may have. Then propane lines are propane lines. As long as there is a good fitting, you can cap the line.

The difficult situation you will face is if the fitting is flared. You would need a female flared cap to rectify the problem and seal off the stove lone. Keep in mind that the flared end may be about 45 degrees. Double-check yours to make sure.

Again, we suggest taking a picture of your fitting and measuring it before buying a replacement. When you are not sure, this is the best way to get the right cap for your stove line. Also, you can cap the line at the outside fitting where the main propane line splits off to direct the gas to different appliances.

How To Cap an Unused Propane Line


The first step is to see what type of fitting you have on the line already. Then the second step is to match the cap to the fitting. That is before you start working on the propane line.

Before you start, you should shut off the main source of propane and if it is the stove you are working on, light the stove and let it burn out. That ensures the line is empty before you start work.

For a Chinook RV, you will need to buy a 3/8 flare plug and use two wrenches to remove the flare fitting from the stove. Then place the cap into the flared fitting and tighten it up.

After tightening, do a soapy water test. If there is a leak simply tighten the cap a little bit more and re-test. Do not over-tighten the cap.

Cap Off Copper Propane Line


The rule of thumb when working with gas lines is to keep the possibilities of leaks inside the RV, etc. to a minimum. The fewer connections inside the trailer, etc., the fewer chances of leaks.

That means with copper lines, you may want to disconnect them at the outside fitting first and then use the appropriate cap to cut the line off from transferring any propane to that appliance.

Or you can cut the line inside and then sweat the fitting and copper line back together then cap it off. But this technique leaves the cap inside and it is best used on hard copper lines, not soft ones.

Sometimes, the best solution is to remove the old lines and replace them with new ones with better caps. The old ones may be damaged in places you are not aware of and replacing them is the only solution.

Do Propane Tanks That Are Removed Need The Line Capped?

Do-Propane-Tanks-That-Ar Removed-Need-The-Line-Capped

This will depend on if you are going to re-use the line again. If you are going to re-attach the propane tank, then the answer would be no you don’t need to do that. However, if you have switched your appliances to non-propane sources, then it is simply best to remove all the propane lines.

That would be the safest step to take unless you see yourself switching back to propane shortly. The lines should be capped not because there may still be gas in the line. that can be remedied quite quickly.

The caps would simply protect your RV from little creatures using the lines to enter your trailer or RV. You may also get some cold air drafts coming through those lines which will make your heater work harder.

But you may not need to cap them if there are shut-off valves positioned in key locations. Just shut them off so there is no clear passageway and your problem should be solved.

Some Final Words

Capping your propane lines is a smart idea when you are not going to be using all of your propane-fueled appliances. It is safe, secure and keeps you from wasting any gas. Just get help from a professional if you are not sure what to do or what cap to use.

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