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Old 06-19-2014, 05:45 PM   #1
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Propane Piping Sizing

I am replacing all the propane plumbing in my 66 Trade Wind. Unfortunately I have already pitched the old copper. Needed $$$.

I believe the main gas pipe is 5/8" ID copper. Then the branches are 1/2" ID flex copper to stove, furnace, fridge and water heater. The NT-30 furnace is 1/2" ID connection. My Atwood 6 gallon water heater has a 3/8" ID fitting to connect to. I don't have a stove or fridge yet, but I will install the lines and cap them off.

Does this sound right?

I understand I can't have any fittings inside the trailer except the connections to appliances. But I have some pretty tight spaces. What is the smallest bend radius for 1/2" ID tubing? I may need an elbow or two here and there to get my lines through the floor.

David
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Old 06-19-2014, 06:18 PM   #2
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David,

We used 1/2" flex copper for the main propane line, and then branched off with 3/8" for all the appliances. More than enough pipe size for everything to run.

You can get a pretty good bend in both 1/2" and 3/8" using a pipe bending spring, or a pipe bending tool like from Yellow Jacket. Avoid elbows. Just another potential place to leak. I used the springs. They slide over the copper line and you can then bend the line without kinking the tube. Be sure to slide the spring off before you flare the tube though. That's a mistake you'll only make once, trust me...

Invest in a good flaring tool. I bought a Yellow Jacket flaring tool after struggling with the cheap ones you can buy at Ace, Menard's, Home Depot, etc. All propane connections on an RV must be a flare fitting.

We also installed PEX pipe over all the copper propane lines under the trailer. 1/2" pex fits over 3/8" copper, and 3/4" pex fits over 1/2" copper.

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Old 06-19-2014, 06:27 PM   #3
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Quote:
Originally Posted by dbj216 View Post
I am replacing all the propane plumbing in my 66 Trade Wind. Unfortunately I have already pitched the old copper. Needed $$$.

I believe the main gas pipe is 5/8" ID copper. Then the branches are 1/2" ID flex copper to stove, furnace, fridge and water heater. The NT-30 furnace is 1/2" ID connection. My Atwood 6 gallon water heater has a 3/8" ID fitting to connect to. I don't have a stove or fridge yet, but I will install the lines and cap them off.

Does this sound right?
I would be surprised if any 5/8" ID copper has been used on any Airstreams. 5/8" OD maybe (same as 1/2" ID or 1/2" copper water pipe) for the initial run from the regulator to the first branch. After that 1/2" OD (3/8" ID) for the rest of the trunk, and branches to the range and furnace. 3/8" OD (1/4" ID) for water heater and fridge.

Quote:
I understand I can't have any fittings inside the trailer except the connections to appliances. But I have some pretty tight spaces. What is the smallest bend radius for 1/2" ID tubing? I may need an elbow or two here and there to get my lines through the floor.
Use smaller line. 1/2" ID (5/8" OD) is difficult to bend to a 12" radius. 1/4" ID you can bend on an automotive brake line bending tool to about a 1.5" radius if you're careful.
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Old 06-19-2014, 08:19 PM   #4
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I would be surprised if any 5/8" ID copper has been used on any Airstreams. 5/8" OD maybe (same as 1/2" ID or 1/2" copper water pipe) for the initial run from the regulator to the first branch. After that 1/2" OD (3/8" ID) for the rest of the trunk, and branches to the range and furnace. 3/8" OD (1/4" ID) for water heater and fridge.



Use smaller line. 1/2" ID (5/8" OD) is difficult to bend to a 12" radius. 1/4" ID you can bend on an automotive brake line bending tool to about a 1.5" radius if you're careful.
I just checked the 2001 22' CCD International LP gas layout and they list 5/8"ID and 3/8"ID as the copper tubing gas line sizes on page F-5.
I think that is what is on my '68 Overlander too.
My LP dealer said the 1/2"ID would work.
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Old 06-20-2014, 05:32 AM   #5
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Thank you very much for your experiences in propane piping. I was unsure if 1/2" piping would be adequate to supply all the appliances at one should that event happen. I will invest in a good tubing bender and see how tight I can get my corners. I will avoid elbows and other fittings inside the trailer.

I won't need to buy the larger piping after all.

David
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Old 06-23-2014, 06:16 AM   #6
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I am plumbing my propane lines in 1/2" ID soft copper, and the branches in 3/8" soft copper except for the furnace which I will run with 1/2" ID as that is the size fitting Suburban sent with it.

I did find a picture I took of my old Trade Wind before I removed the belly pan. It appears the main line was in 5/8" ID copper. I also went down and checked the 86, and it is also in 5/8 ID. All of the branches are run in 3/8" ID.

I am no Propane expert. Maybe Airstream felt the extra volume of the 5/8" ID main line provided pressure and flow stability to the appliances.

None the less, I went with a 1/2" ID main line on my Trade Wind project.

Question: After I finish connecting everything, can I pressurize the system with say 40 psi air and check for leaks? Will the gas valves in the furnace and water heater take this pressure level or will it damage them? It will be a while before I get the new regulator and fill the system with propane.

David
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Old 06-23-2014, 06:29 AM   #7
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I would not do that. The appliances run on .5" water column. 27" is one PSI. You could possible damage something. Good luck.
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Old 06-23-2014, 12:11 PM   #8
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The appliances should be disconnected and the piping capped before pressure testing.
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Old 06-23-2014, 12:25 PM   #9
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I would not do that. The appliances run on .5" water column. 27" is one PSI. You could possible damage something. Good luck.
No, propane pressure at the appliance should be 11" of water pressure, not 0.5 inches.
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Old 06-23-2014, 12:32 PM   #10
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The current terminology used for LP pressure is WG, which stands for water gauge. It used to be called WC,or water column, but was changed to avoid confusion with the WC found on LP tanks, which means water capacity.

Anyway, you are looking for 11" WG, which roughly translates to 0.5 PSI.
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Old 06-23-2014, 01:00 PM   #11
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Sorry for the confusion. What about the 40psi pressure test?
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Old 06-23-2014, 03:00 PM   #12
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I usually do a 20 psi leak down test. Where did you get 40 from?



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Old 06-23-2014, 07:49 PM   #13
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The 40 psi suggested test pressure was what I used to test my fresh water plumbing earlier this spring. I just wanted to test the integrity of my flared connections before hooking up the low pressure propane. I didn't know if the gas valves in the water heater and furnace could take that much pressure. I will not pressurize them per your advice. I'll hook the propane up and go sniffing. Yes, .5 psi, or 11 WG sounds about right for propane delivery pressure.

I'm afraid I got confused on soft copper tube sizing again in post #6 above. They sell tube by ID size, and the fittings for the tubing is sold by OD size. So I used 1/2" OD and 3/8" OD tubing.


I wish there was one convention for labeling copper tubing. I vote for always using the ID of the tube or pipe. That's what matters, how much will it flow. The OD size is just what it is. ABS and PVC pipe is specified by ID size. We never talk about the OD of ABS piping.

Copper tube gets an old guy confused.

David
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Old 06-23-2014, 07:57 PM   #14
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Sorry for the confusion. What about the 40psi pressure test?
If you isolate the line by capping the ends you can test with any pressure under 100psi.
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