Pipe Size Question

[lpigg]

Hello all,

I have read the post here about nat gas pipe sizes and I am still a little confused. I just built a 24 X 28 garage with an upstairs loft. I am getting ready to insulate and drywall the place but have not bought a furnance or anything (it may be a while) but I would like to go ahead and run my gas lines while it is all opened up. I will be running the lines from my house which is about 100 feet away. The only thing that is currently running on this gas line is a gas fire place that gets minimal use. My question is, is it ok to run 1/2 inch to the garage or should I spend the extra $100 and go with 3/4 inch. I will be running it in a underground 4 inch conduit.

Thanks for all the help.

 

[nate379]

Perhaps talk to your gas company?

Here the lines from the meter to anything that uses a good amount of gas, like a heater, are almost always 1".

 

[aandpdan]

The pressures in a gas system are so low, once you get past the regulator, that the size of the pipe is very important.

Coming from an existing service and without a specific type of pipe we can't answer. Don't plan on much with 1/2" or 3/4" though, for a 1/2" water column pressure drop - fittings will reduce these...

At 100'

1/2" about 50,000 btu's/hour.
3/4" about 104,000 btu's/hour

Before you do this, talk to a plumber. It will need to be inspected.

What else is in the conduit? You can bury the piping directly?

 

[lpigg]

Thanks for the response. I was planning on buying the flexible pipe that they have at Menards. I beleive that my current line is 1 inch black pipe and I would connect onto it. The only thing that is in the conduit is a satellite cable and CAT5 cable. I would rather not dig up the backyard again and direct bury. At least that was my thought when I buried the 4in conduit. I have no idea about heating the garage, will 50,000 btu be suffecient? I would like to heat the main floor and upstairs. I am putting R-13 in the walls and r-25 in the ceiling. I also have fanfold insulation on the outside. Thanks for all the help and suggestions.

 

[aandpdan]

There really is a science behind all this.

You need to do a heat loss calculation on the building. It takes into account the size of windows, the doors, the R values, everything. Where you are located is a consideration as well.

I'm not sure about pulling the pipe through the conduit either. While somewhat flexible, 100' is going to be a bear to pull with even just two 90's.

Please talk to your building department/gas company before you attempt this.

 

[lpigg]

Thanks for the help. I will start the calculations to see the requirements.


Also on pulling the pipe through the conduit, there is only 1 45 degree bend in the whole 90 foot run, do you think that this will be possible? If not, I probably won't worry about it until we are ready to actually to purchase a furnance.

Thanks for all the insight.

 

[aandpdan]

What about at the ends of the conduit where it comes above ground? Does it make a 90 there or come straight out of the ground and into a crawl space/basement?

You could always run the pipe in the walls and leave it capped where it is accessible for future use. I'd run at least 3/4". No joints and take pictures in case you don't get this inspected now. If you do need it inspected later they "might" accept your pictures.

You'll need to know the R value on your garage doors too. I'd be interested to know what you come up with.

Its a nice looking building you have there.

 

[lpigg]

I will let you know what I come up with. After reading most of this, I have decided that I will be doing at least a 3/4 inch pipe.

When I said that there are no bends, it is because the conduit starts in the basement and goes straight to the garage. The garage sits about 5 feet lower than the house due to elevation change of the backyard so we just started at the garage and went straight to the house from that depth.

I guess the nice thing about living in small towns are there are no inspections. I had to get a building permit to start the build and that was it. There are no follow up inspections or anything.

I think I am going to run the 3/4 inch from the house and put some excess in the dead space above the loft so I can drop it down later when I decide (afford) to get heat. But I am going to start the figuring on the heat loss so I will know what to look for and hopefully pickup a used furnance somewhere.