Air in the gas line?

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Aug 6, 2018
Reinholds, PA
Can anyone help me out with advice?  I recently installed a "T" in my gas line to run a gas grill or my portable gas fire pit.  The "T" is after the furnace, fridge and stove top but before the water heater.  The water heater is last in line.  Now, my stove top will not lite unless I have the fire pit lit.  If the fire pit is going, the stove will lite in an instant. Once the stove top is lit and I turn off and disconnect the fire pit, the stove top will remain lit but if I turn off the stove top, I can not re-lite it.  My second problem is, the hot water heater will not ignite at all, no clicking noise, no gas, nothing.  The fridge still works and will automatically switch to gas when the electric is turned off.  I'm not sure about the furnace because it's summer I haven't thought to use it.  I understand the I might have other issues with the hot water tank, but the stove top issue is just weird.  I just don't understand.  Any input will be greatly appreciated.

What trailer /motor home is this installed in?? It would seem that you have cut off the gas supply to the stove top and water heater by using the "T" that you did. The appliances are very seldom connected in a single string, one after the other, as you seem to say.

Is this what you used??

This might help:

(The Marshal brand is no longer manufactured but there are others)

If not, you may have used the wrong type of "T". You also need to know what pressure the gas grill and Fire pit require as well. The grills using a small green bottle usually require high pressure as they have a built-in regulator, they will not work well where you seem to have installed it on the low pressure side of your system. (The appliances you listed are all low pressure devices.)
Fire pits normally have their own regulator as well, thus requiring high pressure gas to their feeder hose.  Apparently his gas fire pit works ok, though.

We need to learn more about the Tee you added. Clearly it is interfering somehow. It sounds as though there is some sort of check valve in it that the fire pit holds open and it stays open as long as any gas is flowing. Then closes when it stops (and thus the stove won't re-lite).

If your water heater doesn't even attempt to light (no clicking of the sparker), you have a separate problem there.
Thank you for your replies.  The "T" that I used did not come in a kit.  It is just plain old "T" which I added to the gas line where the hot water tank connects to the gas line.  Off the "T", I connected a propane quick release with a manual valve.  I have added male quick releases to both my portable fire pit and grill so I can change them out quickly.  They both work as they should, no issues there.  So when they are disconnected and the valve at the quick release is turned off, the stove top will not lite and no gas is present.  But all I have to do is lite the fire pit or outside grill , and the stove top will lite instantly.  I don't understand, there no difference between the "T" installed and the valve turned off, and the "T" never being installed, everything should work.  This evening, I will try to post pictures of the "T" connection. 

Regarding the hot water tank, would the igniter still try to lite the system even if there was no gas present?  I do not hear nor smell any gas at the water heater when I flip the hot water gas switch.  I'll have to have my wife flip the switch for me while I'm out side at the water heater.  I'll check to see if a fuse is blown, doesn't the igniter work off the 12 volt system?
The disconnect may be designed to work on the tank side of the regulator, where there's 100 PSI or so of pressure.

The regulator reduces the tank pressure to about 0.5 PSI (11 inches Water Column) to feed the gas lines, and this may not be enough pressure to hold the quick disconnect's seal closed, letting air leak into the gas line when you remove the fuel hose.

The next question is whether the fire pit and grill you're using with the tap want to see tank pressure propane or the much lower line pressure after the regulator.  If you connected the hose in place of their own propane tank so their regulators remain in the circuit, they want to see tank pressure.
First thing I will say is I've seen some "Home brew" Propane modifications and they scare me.

Second I will second the fire pit likely has a regulator of its own so that regulator wants HIGH PRESSURE (Before the RV's regulator) gas. The Stay-A-While (Ask the clerk for an Exten-a-Stay which is the old Marshall Brass name for it) is your BEST and safest option and what I have (The original).

But it is possible to modify the fire pit to work with low pressure.

Now. if the fire pit lights. There is no air in the line.
Thank you very much for your replies Mr. Schneider and John from Detroit.  I have a manual turn valve for use with propane connected just before the quick release. I'm confident that no air is getting into the system and no gas is leaking out.  Both the fire pit and grill work as their suppose to.  It's the stove top in the camper that only lite when the fire pit or the outside grill is connected and lit.
To answer Alfa38User's question.  The trailer is a 2016 Sonic 22' travel trailer.  There is one main metal gas line pipe running from the tanks in the front of the camper all the way to the rear of the camper and the appliances such as the furnace, stove top, refrigerator and hot water tank are connected to this main pipe.  The hot water heater is connected at the end of this pipe in the back.  It is at this connection where I installed the "T".
First, welcome to the Forum!

It sounds like you have it piped in a safe, sane manner, which should have NO EFFECT on the stove with the valve closed.  This is a real puzzle!

Most fire pits and grills require high (tank) pressure LP to function properly.  Your supply line is after the regulator, and clearly a low pressure supply.  Normally, they should NOT be working properly.  Another puzzle!  You have a full right to be confused!!  ??? ???  I am too!

Is it possible the regulator on the tank is malfunctioning??

While your symptoms do not lead this way, try closing the gas at the tank.  Count to 15 then SLOWLY reopen the valve.  This will reset an internal flow valve.

As you can tell, I am grasping at straws, hoping one will fix this!
Both the fire pit and grill work as their suppose to.
Most fire pits and grills require high (tank) pressure LP to function properly.  Your supply line is after the regulator, and clearly a low pressure supply.  Normally, they should NOT be working properly.  Another puzzle!  You have a full right to be confused!!    I am too!

The OP stated that the fire pit and grill work (it lights??)but.... he did not say that he has used the grill to cook anything while using his modified supply. IMHO and experience, they will always light as there is sufficient propane at low pressure for that, but trying to cook that steak on a grill that requires high pressure (green bottle type) will be  a disappointment and a ruined steak. The reason is that the green bottles are a high pressure supply and a grill that uses them has a regulator built in. Two regulators (one at the gas bottle and one in the BBQ) will result in a poorly performing grill even though it lights. Then again, I don't remember him identifying what kind of grill he is working with, a high or low pressure type.

As to a fire ring, I can only imagine how those are used, as I have never had one. The one shown in the video above seems to be a low pressure device. If it is really a high pressure device, it will light but the heat produced will be considerably less than normal, just like the a BBQ.

To me as well, everything seems to be correctly connected BUT from his description, it seems that the propane is no longer reaching  the stove top nor the water heater properly with his modification in place. Are all the fittings (shutoffs) used meant for use with a PROPANE supply and not just water??

Grashey's suggestion of  closing and then opening the tank valve is a good one but the OP may be obliged to do this each time the he changes the supply from trailer to grill or grill to trailer as well. The portable bottles and motor home tanks do have a valve that closes down the supply if it THINKS there may be big leak (higher flow than expected) and that addition plumbing may cause that to happen on occasion.

The answer may be to use a kit described above (Ad and video) and mount it next to the bottle in the front. I know, kinda $$ but..... it is the right tool for the job.
Thank you for your replies.  Fire pit and grill work as they should.  Fire pit puts out a nice amount of heat and steaks are no problem for the grill.  I think I might have mislead.  The "T" connection was made in the middle last season and everything worked fine.  The issues started in this current season, during my first trip out.

Update:  Hot water tank now works regardless if the fire pit is connected and lit.  I do believe that was an electrical connection issue.  The igniter is now working and the hot water heater fires right up.  I tested the furnace last evening and found that it has the same symptoms as the stove top, it will only lite when the fire pit is connected and lit.  I discovered the furnace and the stove top is connected to the main fuel line at the same location, using a "T".  Now the fridge which is 12" further down the main fuel line, has started doing the same thing as the furnace and stove top.  Once these appliances are lit they work fine.  But if I disconnect the fire pit, they continue to work fine , but if they cycle off they will not re-lite.  One propane tank is completely full and the second tank is at approximately 20% and I have the automatic "switch over" fuel regulator and the arrow is pointing to the 20% tank.  Both tanks are open and no orange is showing in the sight window of the regulator, its all black.  It shouldn't make a difference but I will try refilling the 20% tank.  If that doesn't do anything, I guess I'll try replacing the regulator and then finally, if all else fails, I'll head to my local RV service department.  Thanks again.

Here are some pics.


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Since it was working ok for awhile, about the only thing I can think of is that the firepit and wter heater are high-volume gas suckers and it sort of pulls gas through the piping, whereas the stove is a low volume appliance.  Maybe some sort of blockage, e.g. an oily gob of mercaptan?  But it's all very low pressure - 11 WC inches is only about 0.5 psi.

Will the stove light if the water heater burner is running but not the fire pit?  If so, it can probably be concluded that the flow volume is what mkes the difference, not the fire pit itself.

The problem may be in the branch line to the stove or the stove itself, even though it is affected by the other appliances.  Do you have any way to connect the stove line to another source to test it by itself?


Try changing the regulator (arrow) to use the full tank and see what happens. I have seen some unexplained things happen with that change over device at times and I have a reasonably new one, changed 2 years ago. I think the oil used (mercaptan) in propane to add the smell kinda screws them up.

I would have thought that under the trailer the pipe would be iron and only the feed to to appliances themselves would be copper. Copper would be too easily damaged by road debris IMHO.
To answer Mr. Gary's questions, the stove will not light when the hot water heater is burning.  I might have the correct fittings, so I could try to disconnect the stove and furnace lines from the main cast iron pipe and use a hose line with it's own regulator and see what happens.

To answer Alfa38User questions, I have tried switching the regulator arrow to no avail but I can give it another try.  And yes, your are correct, there is a cast iron pipe underneath that runs the length of the trailer and only the feed to the appliances are copper.  The very end of the cast iron pipe is where the hot water heater is connected and that is where I installed the "T" for use with the outside grill and fire pit.
Below is the link for the fire pit.

Is it possible that's the gas pressure is to high and the regulator isn't working properly and the stove top, furnace and the fridge have check valves that close until the fire pit is lit which reduces the pressure and values then open up?

I have to return the camper to it's storage area for the next week or two, I'll report back any news once I try your suggestions.

Thanks again.
Ok, I'm back.  Latest up date.  To no avail, I filled the propane tanks and headed out camping. Though I was happy the fridge came on when I unplugged the electric.  Still no change in the stove top.  So when I got back home and order another regulator.  Though I was a little hesitant to order the same one, I did it anyway for simplicity.  Turned the tanks on slowly and Lord and behold, the stove top fired right up.  I still don't understand but problem solved.  Thanks to everyone who offered advice.
My GUESS is that before it worked, there WAS air in the line.  If the tank valve is opened too quickly, it sees a rush of gas and assumes a leak, and reduces flow to a minimum.  Apparently, this minimum was enough to run the refrigerator, but not the stove.  Turn tanks off for travel.  This resets the flow stop safety.  Open slowly, no rush, no flow restriction.  All works.
I am inclined to agree with Preacher Gordon.  Excess flow valve. though I'm surprised it allowed enough flow for the water heater.. That is a "Major" appliance as Propane goes.

Might have been a bad reguator in which case you fixed it.

Air in the line can be an issue for the FRIDGE as it is a "minor" sucker or the oven (Pilot lighting) but for the stove top furnace, or water heater. these suck so much propane that any air-in-line will be cleared before .. Well before the burner lights (stove top) or 2nd attempt on the DSI Furnace or water heater.  In fact the propane already in the line will be gone by the 2nd attempt and fresh from the tank replacing it,, that is if it needs a 2nd attempt.

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