Right size gas piping?

Luke4 · November 2022

I'm looking to run a new gas line in my crawl space in place of my old one. It is currently a 1/2 in pipe that stops at my water heater, but I am going to have a new 2 ton heater in my attic further down the line. The gas line will service my 3.5 ton furnace/ gas fireplace, 50 gallon water heater, 2 ton 40k btu heater, and my dryer.

Is 3/4 in gas pipe enough pressure to serve all those units? Roughly 60 feet or so to last heater, with a couple 15 foot detours for fireplace and first heater.

Ironman · November 2022

First, is this LP or natural gas?

You need to add up all the btu ratings of the appliances (no such thing as 3.5 ton gas furnace as far as btus are concerned), then determine the total developed length of the line. From there use the proper sizing table to determine what size line is needed.

I seriously doubt that a 3/4” line would be sufficient and even that can be vague because a 3/4” black steel pipe will carry much more than 3/4” CSST or 3/4 copper.

Luke4 · November 2022

This is Natural Gas, and haha yes I realized that before posting I didn't have the BTU rating of that system, so I just sent an approximate size. I'd imagine it's 60-80k btu, but can drive over and check tomorrow.

I was planning on using black steel piping if that helps.

Ironman · November 2022

So, you’re looking at least 250k btus? How long is the total developed length from the meter to the last appliance?

I can assure you that a 3/4” line isn’t gonna come close to carrying it.

EdTheHeaterMan · November 2022

This might help
https://www.edcgov.us/Government/building/documents/Gas Pipe Sizing (Natural).pdf
Or this video

https://www.youtube.com/watch?v=1fpy9NrE21c

EBEBRATT-Ed · November 2022

3/4" is not nearly big enough.

You need to find the BTU ratings of all gas appliances to be connected and the length of run from the meter to the furthest appliance. The # of elbows and tees need to be considered if they are more than the average amount and you need to be sure your gas meter is large

JUGHNE · November 2022

What is the pressure of your inside gas service?

4-6 Ounces....or 2 pounds per square inch.

PC7060 · November 2022

Here a link to the gas code with instructions for total developed length .

https://www.edcgov.us/Government/building/documents/Gas%20Pipe%20Sizing%20%28Natural%29.pdf

Luke4 · November 2022

Thanks guys for all of your help. That video was exactly what I was looking for - I had found the tables but didn't quite know the particulars of how to read them.

Is there an easy way to check and find out the pressure? If not, I'll check the regulator or meter / call the gas company tomorrow. Edit From a simple google, it said their standard is 5.3 oz or 9.17” w.c.

Also do you all have a preferred product you use when securing the pipe to the joists?

EBEBRATT-Ed · November 2022

As far as hangers go you can go with the best which is threaded rod with Sammy's screwed into the wood with 3/8" rod and Clevis or band hangers. This is a system you can adjust. You can also use side beam hangers or F & M plates on the top.

Or you can use wire hangers nailed into the joists or two hole pipe clips but not any adjustment when their installed.

I suppose some would use plumbers strap with all the holes in it but it makes a crappy looking job. I only used that for a temporary job

EdTheHeaterMan · November 2022

Luke4 said:
Thanks guys for all of your help. That video was exactly what I was looking for...
...Also do you all have a preferred product you use when securing the pipe to the joists?

Duct tape, bubble gum and string.

Luke4 · November 2022

Ebebratt - Can you send me an example of a threaded rod with sammy's screwed in? I don't like the strapping with the holes in it as well.

Do you have experience with something like this? - https://www.homedepot.com/p/The-Plumber-s-Choice-1-in-Half-Clamp-J-Hook-with-Nail-for-PEX-Tubing-Pipe-Support-50-Pack-HC00150/306307285?g_store=&source=shoppingads&locale=en-US&pla&mtc=SHOPPING-BF-CDP-GGL-Multi-Multi-NA-NA-NA-PLALIA-NA-NA-NA-NA-NBR-NA-NA-NA-LINC_Lapsed&cm_mmc=SHOPPING-BF-CDP-GGL-Multi-Multi-NA-NA-NA-PLALIA-NA-NA-NA-NA-NBR-NA-NA-NA-LINC_Lapsed-71700000100310360-58700008031441221-92700073051609756&gclid=CjwKCAiAjs2bBhACEiwALTBWZZBvLNmAEb5-RI9ZD4KiXbQTkVdj55YevOPqkvfNcOccAjFgxLrXURoCHgQQAvD_BwE&gclsrc=aw.ds

EBEBRATT-Ed said:

Gilmorrie · November 2022

As already stated, it depends upon the Btu/hr demand of the new furnace and other connected appliances - and the configuration of the piping, number of fittings, etc. Your gas company may be willing to come out and advise you. The meter's size itself needs to be verified, too.

Here's another calculator: http://snowcrest.net/thriftysupply/pdf/NAT-LP-PIPE-SIZE.pdf

EdTheHeaterMan · November 2022

Luke4 said:
Can you send me an example of a threaded rod with sammy's screwed in? I don't like the strapping with the holes in it as well.

That one nail PEX support is not recommended for iron pipe. Unless you put one every 16". also the fittings at each end of the pipe will not allow the pipe to be against the surface (unless it is open joist with no sheetrock).

Sammys are for ceiling joist in stead of using flanges https://www.supplyhouse.com/Sioux-Chief-590-4411-GST20-2-Vertical-Sammy-for-Wood-Applications-3-8-Rod-Box-of-25
then all thread rod to a split ring hanger https://www.supplyhouse.com/Bluefin-GVSR075-3-4-Electro-Galvanized-Split-Ring-Extension-Hanger-Non-Hinged

JUGHNE · November 2022

For black iron pipe up against the floor joists, I use 2 hole steel straps sized for rigid galvanized electrical conduit.

Usually a fitting is wanted to end up being between joists.

If the pipe must be hung below joists then the Sammie screws or "Sidewinders" with the rod and clevis hanger would be used.....as the two Eds noted above.

There is also a one piece steel hanger that clamps the pipe and has a strap with holes in it.
Looks OK.

I would never use any plastic hangers for gas pipe.

Right size gas piping?

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