Natural Gas Pipe Sizing question

EddieWalker · Jul 17, 2021

I'm in a long, drawn out process of adding on and remodeling my house. One of the things I'm doing is adding Natural Gas to my house. I have the gas line next to my house, but I haven't built my garage yet, which is where the line will come into my house. I plan on having a manifold in the garage attic to distribute the Natural Gas to my kitchen stove, water heater, HVAC, BBQ and probably a stand by generator.

Here in Texas, you have to be a licensed plumber to buy the yellow colored stainless steel lines. That is an option, but one I'm trying to avoid since the garage isn't built yet.

I'm getting close to finishing off the ceiling of my back porch. Before I do this, I want to run a line to the BBQ.

I've used black iron pipe several times and I have a pipe threader for half inch and 3/4 inch pipe. I'm very comfortable running black pipe for the gas line.

My question comes from reading online on what size pipe to run. I was going to run half inch, but then got confused with what I read online, and the recommendations to go with one inch and even 1 1/4 inch pipe. It's a simple 3 burner BBQ. If it dies, it will be replaced with another 3 burner BBQ. This has proven to be more then enough grill for us.

The hose off of the Propane tank isn't even close to as big as a half inch pipe.

I'm planning on using 5 sticks of pipe that are 10 feet long. This will be capped in my attic for now, and then another ten feet to where the manifold will be in the garage attic. 60 feet total run from the manifold when it's done.

Can I use half in pipe or is there a reason to go bigger?

It is legal in TX for a home owner to run their own Natural Gas lines, but it does have to be tested and certified by a licensed plumber. I've been through this process a few times, and I've always passed the first time.

This is my porch ceiling so far. I need 37 more cedar boards, but I'm hating that they have become so expensive.

oosik · Jul 17, 2021

Around here cedar has never been cheap. I can only imagine what it costs now. BTW - that makes a beautiful ceiling.

Natural gas was "THE" fuel when we lived in Anchorage. Dirt cheap and all new subdivisions had gas.

As I remember - the yellow line running to our house was one inch. I would imagine it depends upon the pressures the gas company runs their main lines at.

Menagerie-Manor · Jul 17, 2021

1/2" is sufficient for a normal gas grill.

ponytug · Jul 17, 2021

Your porch looks gorgeous!

Two minor items, neither of which totally answers your question:

Corrosion: around here all buried gas lines have plastic over wrap to reduce corrosion. Who wants a gas leak? Can you get plastic coated pipe for gas?
Gas has a relatively low pressure in distribution pipes. So that means much larger pipes compared to water, or compressed air.

The generator alone will probably need at least 1 1/4" back to a large enough regulator (I would check the installation guide for the size you are thinking about.). Many require (suggest?) a separate regulator just for the generator to keep from disrupting things like pilot lights on water heaters. Personally, I would plan on a second regulator for the generator.

FWIW: here is a cheat sheet to compute appropriate pipe sizing. 1/2" looks small to me for most modern BBQs.

All the best,

Peter

dlctcg · Jul 17, 2021

Eddie... I agree with @Menagerie-Manor...

We use Trac-Pipe here (not the Yellow stuff)...

But if I looked up steel pipe sizing correctly 1/2" on natural gas with up to an 80' run would be good for aprox. 40,000 - 42,000 BTU's... This doesn't account for fitting lose... etc
3/4" would be closer to 90,000 - 95,000BTU

I'm guessing your 3 burner Grill is closer to 27,000 - 30,000BTU's

Menagerie-Manor · Jul 17, 2021

ponytug said:
Your porch looks gorgeous!

Two minor items, neither of which totally answers your question:

Corrosion: around here all buried gas lines have plastic over wrap to reduce corrosion. Who wants a gas leak? Can you get plastic coated pipe for gas?

Gas has a relatively low pressure in distribution pipes. So that means much larger pipes compared to water, or compressed air.

The generator alone will probably need at least 1 1/4" back to a large enough regulator (I would check the installation guide for the size you are thinking about.). Many require (suggest?) a separate regulator just for the generator to keep from disrupting things like pilot lights on water heaters. Personally, I would plan on a second regulator for the generator.

FWIW: here is a cheat sheet to compute appropriate pipe sizing. 1/2" looks small to me for most modern BBQs.

All the best,

Peter

Being trade I can tell you that a 1/2" supply using normal gas pressures will run away with any std gas grill. My last 3 grills were piped in with 3/8 od soft copper without any issues.

ArlyA · Jul 17, 2021

ponytug said:
Your porch looks gorgeous!

Two minor items, neither of which totally answers your question:

Corrosion: around here all buried gas lines have plastic over wrap to reduce corrosion. Who wants a gas leak? Can you get plastic coated pipe for gas?

Gas has a relatively low pressure in distribution pipes. So that means much larger pipes compared to water, or compressed air.

The generator alone will probably need at least 1 1/4" back to a large enough regulator (I would check the installation guide for the size you are thinking about.). Many require (suggest?) a separate regulator just for the generator to keep from disrupting things like pilot lights on water heaters. Personally, I would plan on a second regulator for the generator.

FWIW: here is a cheat sheet to compute appropriate pipe sizing. 1/2" looks small to me for most modern BBQs.

All the best,

Peter

Are you sure that's "plastic covered pipe"?? Here, all the main natural gas lines are 100% HDPE ak plastic. Lines in homes are steel and certified as gas pipe. All pipes wear out from electrolysis, not rust. Plastic seems to be much better at not doing that.

cdaigle430 · Jul 17, 2021

i am no expert but you will have to make sure with all the appliances you will run that yourmain service coming into you home is at least 7 water columns.

This refers to the amount of pressure it takes to raise a column of water 1 inch. There are 27.7 inches of water column (wc) pressure in 1 PSI of pressure. So 7"wc is about 1/4 PSI. This is the normal pressure that household natural gas is delivered.

I just switched over to Natural gas to heat my home and run a standby generator (16KW) was told that if you dont have enough WC coming in youll have trouble...so they recommended at least 7WC when the utility company ran the line to my home. I have 3/4 black iron to my home.

As for the BBQ only-find out what the WC requirements are and google size WC and pipe size requirements.

Larry Caldwell · Jul 17, 2021

The length of the run will make a big difference, and your biggest draw will probably be the generator. I did a remodel once where the backup power for a lab was a NG Ford V8 fed by a 2" line. We had to move the regulator which added a long (150'?) run to the engine. We had to up the size of the line to 3" to shove enough gas through it. The engine would start OK, but starved for fuel under heavy load.

The size of the orifice in the regulator can be another pinch point.

ponytug · Jul 17, 2021

ArlyA said:
Are you sure that's "plastic covered pipe"?? Here, all the main natural gas lines are 100% HDPE ak plastic. Lines in homes are steel and certified as gas pipe. All pipes wear out from electrolysis, not rust. Plastic seems to be much better at not doing that.

You are right. The high pressure distribution lines around here are plastic, too, cross-linked HDPE for the most part. What @EddieWalker wants to do is downstream of the regulator, where the pressure is typically 7" of water column (WC, which translates to 0.25psi) For distribution around the house, the pipes tend to be black iron pipe extruded with a PVC cover, or copper of the same design. "Tend to be"... Inside tend to be black iron pipe.

I am no code expert, but I would be surprised if any code permitted plastic inside the home. Some jurisdictions don't permit soldered copper either. California doesn't permit plastic, without written permission from the state, and galvanic protection other than zinc galvanizing is required for buried lines.

High pressure gas lines for transmission tend to be 500-1,000psi, those yellow, or black cross linked HDPE pipes run 100-150psi, so it is a big step down to be at 0.25psi in the house, which is why pipes tend to be large to handle the surges in demand (water heater coming on, furnace, BBQ, etc.) without much pressure drop elsewhere in the system. That is why the cheat sheet that I mentioned above is all about distance and BTU demand.

Like @Larry Caldwell, I had a neighbor with terrible trouble getting a standby generator to work, (seven months of trial and error, and not working), much (all?) of the problem was a few feet of undersized pipe that starved the generator under load. The installer really didn't want to redo the pipe and valve, from 1" to 1 1/4", but as soon as he replaced them, the generator worked. What was specified in the installation manual? 1 1/4" pipe.

All the best,

Peter