Underground gas line help?

[flusher]

What should have been a simple job got complicated yesterday: we finally got around to buying our own 120 gal. propane tank, and after they switched out the old rental tank, a pressure test showed an underground leak somewhere between from where the 1/2" copper line went into the ground and where it came out 120' latter, to a regulator set at the side of the house. the tank sits at the back of a shop building, where a second regulator supplies a propane direct vent heater. Having the tank there, and not at the house, works out better in many ways. The line was buried about 3' deep in a 16" wide trench with an electrical conduit and plastic water line about 10 years ago. Since the leak only showed up under a high pressure test, and I never suspected a leak otherwise, and we couldn't find it using a gas detector wand, looks like I will need to retrench and bury a new line next to the old one. Far enough away that I don't hit anything, of course. I am thinking I should pull it thru 2" PVC conduit? I have never trenched anything, and going across a well-established gravel drive concerns me- will a rental trencher handle that? The gas guys said to bury it 18" deep. A little research says that any concealed joint should be brazed- and since coils of type L copper come 60', I will need one joint. The original joint was a flare fitting, I recall, but its hard to imagine that coming open... still?
Comments/advice are welcome!

When my propane line went in 5 years ago I had two choices per the propane supplier--plastic pipe or black iron pipe. I chose iron pipe because of the moles, gophers and ground squirrels that inhabit my almond orchard. So far so good.

 

[Danno1]

That is very interesting! I like using conduit, but would probably not have thought of the potential gas accumulation issue - man, that could be dangerous! Now, I know to avoid conduit when I run a gas line...

Can it be vented???


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[hr3]

Here in Maine running a gas line in conduit is allowed ,, We do alot of generator installs and alot of the gas people like doing it that way,,

If the ends of the pipe were open how is the gas going to build up ???

 

[BXpanded]

I've installed literally hundreds of miles of pipe and cable from tiny little 4 wire telephone drops to 48 inch water mains. Pipe and cable are not considered temporary. If the cable or pipe is rated for direct burial, it does not need conduit, etc. It is designed for many, many years of use when installed as intended. Placing a direct burial cable or pipe inside conduit can constitute improper installation. Save your money, do it right. "Right" is according to the manufacturer's instructions.

BTW, Gas lines inside a conduit really offer no explosion hazard. Three things are necessary for combusion or explosion:
1) Fuel- if the line leaks inside the conduit fuel will indeed be present.
2) Oxygen- if the gas line leaks the gas will displace much oxygen and create a rich, oxygen deficient mixture in the conduit that can't burn.
3) Ignition source- not many sparks or open flames inside an underground conduit.

As an example of a non-combustible rich mixture, when no inert gas was available and I needed to solder a fitting with no oxidation permitted inside, I've used natural gas or propane to purge the line. No oxygen, no fire and no oxidation inside the pipe. Works well with HVAC lines where a small piece of scale can cause problems.

 

[Egon]

[QUOTECan it be vented???][/QUOTE]

Natural gas can be vented. There are guidelines for this on road crossings and such.

Propane is a little harder to vent. It's heavier than air. Therefore a whole different set of guide lines will prevail.:thumbsup:

 

[handirifle]

I just moved into my new house this march. My propane tank is about 100' away and we used the yellow plastic line. This stuff is very tuff, and I highly recommend it. As for the copper, and the soldered joint underground, I say no way. No telling how or what chemicals migh react with the solder. As for laying it yourself, here, I dug the trench with a rented ditch witch ($165 a day) in one day, and the propane company laid the line. They provided the line, and I paid a flat fee. If memory serves me, it was about $175. Keep in mind mine is a rented tank and they fill it when needed, so they have a vested interest. BUT, they would have done the same, had I bought the tank also.

If soils are acidic, they could wreck havoc with copper lines and any soldered joints. I got my degree in heating and airconditioning and refrigeration, as well as business administration, and then spent 5 years doing field repairs of same. I saw many copper lines from propane tanks with leaks. In fact depending on where you live, chemicals in the air can eat copper joints.

Yes, I suppose a gopher COULD chew through the plastic, but it's 24" deep, not sure how deep they (gophers) go, but it is a LOT more resistant to vibration, and WAY easier to lay than conduit, or especially copper IN conduit, there would be no issues with the 45 deg or 90 deg. In the case of nicking a line while trenching for something else, I fell the plastic line would be way less to kink or crack than copper.

I live in the Central Coast area of California, and here they are fire and earthquake paranoid, with good reason, I might add. That said, the plastic is the ONLY thing they will approve underground. Just know, if you do it ALL yourself, there are special connectors to connect the plastic to rigid line, and special tools to do it with, thus why I let the gas company do it. When I looked into it, the cost of the gas line itself was almost the total job cost.

 

[Egon]

Just know, if you do it ALL yourself, there are special connectors to connect the plastic to rigid line, and special tools to do it with

When I purchased some plastic gas line the supplier installed the end fittings in his shop. That cost quite a bit more than just the pipe itself.

 

[varmint]

I found out that the normal "citizen" can't buy the plastic gas line around here. The propane company guys suggested the casing- I had worried about a leak and the conduit filling with gas, too. But, it seems that a casing in SOP in many cases. A contractor friend in Indiana tells me they use casings. I guess you could sniff gas, and I think I will seal the ends where the copper comes out, to keep moisture and critters out. Still learning.