Plumbing and Piping - what size gas line to put under ground?

I'm going to bury a gas line under ground from the meter to the garage. About 100'. I plan on using a gas furnace to heat the two story garage which is about 450' per floor. the salesman from the gas company said I may need a 2" pipe because of the low pressure up here but I wanted some more info from you guys before I call them back and ask for engineering. The utility uses plastic line under ground. Will this type of pipe be available at the local plumbing supply? I have some charts that show pressure drop for different water piping but nothing for gas.
Thanks in advance

Start by checking you local codes.
Many jurisdictions do not permit homeowners to run gas lines.

The size of the line is computed by rated demand load and compensated for length of run.

If you use iron pipe underground it must be factory wrapped except- field wrapping is permitted on fittings.

If an underground iron pipe is connect to an above groound iron pipe you are required to have a dielectric fitting a minimum of 6 inches above grade.

Above grade iron pipe requires bonding (electrical grounding)

Minimum burial depth is 12 inches (18 inches for plastic- but check local codes on this because many require the line below frost line.)

If running a plastic line you are required to lay an AWG # 18 Yellow insulated tracer wire.

If runnig plastic undergorund it must have a 30 inch iron section before turning vertical and the vertical riser must be iron pipe.

May not be buried under slab unless sleeved in schedule 40 steel, iron or plastic pipe with interior end of sleeve sealed. The sleeve must have an approved outdoor vent a minimum of 4 inches above grade.

All fittings used on gas lines must be approved for gas.

I have been told by the zoning officer that my township recently adopted the IRC 2003. I'm sure everything is in there except maybe whether or not I can do it myself. I don't know what I'm puttin in there for a furnace yet so I was hoping to just make sure that the line to cover the 100' was overkill. I was just hoping to get things in the ground before the frost so I could do some work out there over the winter but it may just have to wait for the spring so I can get all my ducks in a row.

Your going to have to come up with some kind of btu load that you will have out there for the size pipe you need. While you at it, Id check code for there on just how high you have to put the open flame of the furnace off the floor. Out there in the garage. Here its 2' , up in canada some say 5' off the floor for the flame.

ED ;)

what's the concern with that? I've never heard of that before, but then again it's not my business. Thanks for the warning.

Natural Gas, Propane, Gasoline and other flammable products are heavier than air and settle to the floor. All gas appliances with open flame must be at a minimum height off the floor to prevent an explosion and fire. This is in the plumbing code and varies from state to state. In California for example most water heaters are in the garage and must be raised so that the burner is at a minimum of 18" off the floor. Other states require two feet or higher.

When installing a water heater in a garage it must also be installed outside the traffic flow pattern or be protected by and approved barrier.

I don't think that will be a problem. All of the mechanicals will be raised into the far left corner by the chimney. No traffic flow. I'm planning on an on-demand coil in the boiler or stand alone if I do forced hot air. There will be so little hot water used out there that I'm willing to deal with the downside of on-demand to save the space and costs. We have an on demand coil in the oil fired boiler in the house and it works OK. I would like to find a more reponsive mixing valve to put on the outlet but that's for another discussion. Damn can that thing get hot though.

What's more of a problem is the lack of pressure on the hot water. The main drops for 3/4" to 1/2" right after the meter. so the everything is branched off of this 1/2" line. That and the 3.5 GPM restricter leave minimal hot water presure on the second floor.

Speedy, We can put this question to rest very quickly if you will contact your gas supplier and ask them what pressure they run on their mains and the specific gravity based on pressure drop. It is apparent you have not received the answer to your question on supply size from meter, but this can not be calculated with out the above information. Also if you will post back with the distance from your meter to the most remote gas line in your system you will be impressed how quickly you get the answer you seek. Good Luck and post back soon.
Richard

Ok, I'm running ragged the next couple of weeks but I'll get a call into them as soon as I can. Thanks for all the help. Someday I'll pay one of you people to do all of this stuff for me but the first time around I want to do as much as I can myself just to see how it all goes together.

Speedy, If it were all about money I don’t think any of the plumbers would take the time to post here. I admire anyone that takes the time research a project and put effort into it. I don’t think these people are going to put me out of work. You should be very proud of any thing you can do at your home on your own. I just overhauled an engine, never had before, research, forums, a book and presto it runs fantastic. Didn’t have too, but saved a few thousand and oh the pride I felt.
Post back with the info and I know you can handle this.
Richard.