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Old 01-06-2011, 03:37 PM   #1
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Buried gas pipe in conduit


Let me just start with some CYA, first the intent of this post is to ask for corroboration or correction on what I've found in my research on a project that is likely at least 4 or 5 months off.

I've searched here and read what I can find of pertinent International Fuel Code. Before I start this project, just as I have and will with any of my other projects, I will be pulling permits with my city and performing all due diligence - and this post is one aspect of that due diligence (and not the only aspect).

I've done gas pipes, always under permit and with inspection.

This time around, I'm planning a gas pipe to the garage. There is a pipe already run underground, as is there also electrical, but neither instills confidence in me - I've disconnected the gas in the house as it connected near the waterheater with a flexible copper line that connected to fittings before going through galvenized pipe in the ground. And the copper pipe was kinked inside the house.

The plan is eventually that I'll be getting a new high efficiency heater, which I'll also be locating in the utility instead of the current location of the crawlspace - plus adding central air. The current heater is an 83% efficient unit, it's less than 10 years old and I think it would be ideal for the garage. But the heating of the garage will likely be at a later time than the gas pipe run. What I will be doing sooner is running a new trench for a new feeder for a 100 amp subpanel (I restore old cars, and plan to operate a large compressor and welder, plus want the garage well lit for body work)

Before I ever did my first gas pipeline for natural gas in a home context, I had been plumbing gasoline hoses in cars on a hobbyist basis for a couple decades, culminating in high pressure gasoline systems designed from scratch for custom built fuel injection systems in formula-style race vehicles for a student engineering competition. I credit the latter for being my best source of experience in understanding what does and doesn't work for getting a pipe joint that doesn't leak. And yes I know there is a difference between gas and liquid.

I am aware that gas piping is allowed under permit in my city, I've done it. Hopefully anyone reading this bears in mind the importance of performing due diligence and assessing whether their level of experience is appropriate to this kind of work.

So with the CYA out of the way, here's my question:

I think what I've gathered as far as one of the best practices for buried gas pipes is black steel inside conduit. I've had to look at adaptations outside of Michigan to get more detail, and I'm assuming that Michigan might be less restrictive but I'm inclined to try to do this following more restrictive guidelines to ensure the most safe installation possible...

So by black steel in conduit, say I'm running a 3/4" pipe to the garage... Code seems to say the conduit has to be at least 1/2" larger than the pipe OD, 3/4" pipe is 1" OD and any coupling fittings would make it larger, so 2" should be a size that would definitely be large enough... Schedule 40 white plumbing PVC would be an appropriate conduit, or should the conduit be electrical? I'm assuming the intent is watertight and plumbing PVC would be better since I don't think electrical is really counted as watertight.

I've also read some states want 12" radial seperation from electrical. So if I was to achieve that, would it be appropriate to also run the electrical in seperate conduit, make the trench 30" deep, lay the gas at the bottom and suspend the electrical at 18" deep to maintain seperation until the trench is backfilled?

And my understanding is the conduit is to run into the interior on both ends.. Is there something that can seal the gap between conduit and gas pipe so that any leak doesn't enter into the buildings? I'd think expansion foam would still be porous to let gas through, and I'd think some sort of venting to outside would be prudent...

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Old 01-06-2011, 05:48 PM   #2
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Buried gas pipe in conduit


The only one that can answer your questions is your local jurisdiction, the rules are different depending on what code they are using and whether they have modified it sorry.

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Old 01-06-2011, 05:53 PM   #3
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Buried gas pipe in conduit


this is what I use for underground gas lines http://www.wal-rich.com/YellowPolypipe.pdf
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Old 01-07-2011, 08:07 AM   #4
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Buried gas pipe in conduit


I would definitely be all for plastic such as that, being a person that's dealt with his share of rust in cars and being that I'm a believer in appropriately graded plastic where corrosion of metallic piping is expected.. And I wouldn't mind the requirement to put a wire on for locating the pipe underground, but what I am uncomfortable with is the idea that the plastic can only be used underground and the riser has to be metal. I get that it's for damage protection, but I'm using plastic so it doesn't corrode and nevertheless I'm required to use metal underground anyway?

If the plastic pipe is being used, would it be allowed to use the plastic until above ground if it was inside conduit for protection? Preferably schedule 40 PVC.

And as far as what the AHJ allows... I haven't spoken with my current city inspector about underground gas pipe yet, and as I said this is planning for a future project at this point. I have an inspection coming up with him on another project I have ready for inspection inside the house, so I'll have a good opportunity to discuss it with him next week. 2 houses ago, I lived in the suburb right next to where I lived and it was practically anything goes and I'll leave it at that. I guess what I'm looking something better than minimum, something that is universally accepted.

But what I do know is that local jurisdiction adopts by reference the state fuel gas code without modification, and Michigan uses 2006 International Fuel Gas Code by reference without modification, as does the state of Michigan.

Last edited by WillK; 01-07-2011 at 09:04 AM.
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Old 01-07-2011, 12:50 PM   #5
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Buried gas pipe in conduit


Just a bit of an update... I just did some research with our gas company, apparently for the do it yourselfer, you can purchase pre-assembled polyethylene fuel gas lines. I think this really sounds like the best way to go as far as ensuring I get the best underground line possible.

http://www.consumersenergy.com/content.aspx?id=1201
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