Natural Gas Pipe Sizing question

   / Natural Gas Pipe Sizing question #11  
You really need to check with the local gas company to be sure you know what their delivery pressure is. You might even want to get one of their servicepeople or service supervisors to take a look at a sketch of your house piping and size it for you.

As mentioned above, 7" w.c. is a typical delivery pressure, BUT it's also VERY common for the gas company to deliver 2# (2 pounds) of pressure when the house piping will be run with CSST (Corrugated Stainless Steel Tubing). (That's the yellow tubing you referred to.) The reason for this is that CSST is measured OD instead of ID, it's expensive, the fittings are expensive, and the corrugations add some restriction. So in order to be able to run a SMALLER size in CSST (as opposed to black iron pipe), the delivery pressure is increased. Lots of new subdivisions are entirely 2# (PSIG) delivery now for this reason.

Also, you mentioned that "manifold" in the attic. If you're talking about the actual manifold where you'll run all your CSST branch lines to feed from, you're going to want to put that someplace more accessible. Otherwise a residential piping system wouldn't really have a "manifold". You have a main line and then branch off of that with drops (tees) as needed.

The installation requirements for CSST are defined in the manufacturers installation instructions in detail. The National Fuel Gas Code, NFPA-54 also has requirements for every material.
With CSST you have to install protective strike-plates where it penetrates framing, etc. You need to clearly understand both and be sure you know what pressure your gas company is going to deliver before you'll know how to size it. Most everywhere you have to be "certified" to run CSST. What "certified" means varies by locale.

If you're just wanting to pipe with black iron, you might be able to do the work. Here where I'm at the gas company would just inspect visually (before it's covered) and do a final pressure check. You wouldn't even need a plumber if you're doing it on your own home. This varies by locale and gas company too.

Find out what they plan to deliver. If it's 7" w.c., you'll be surprised how much pressure drop a 60' run of 1/2" pipe will take. The entire system is supposed to be sized so that you reach each appliance with only 0.5" w.c. pressure drop. That's not 0.5" drop for each branch or pipe segment -- that's total from the meter to the farthest appliance. That's by the book.

These sizing tables are readily available -- just be sure you're looking at the heading on the table and it reflects the correct delivery pressure, pressure drop, specific gravity for natural gas, and pipe material.

Sounds like there's no question that you can install the pipe. But the last thing you want is for the visual or final inspection to turn you down because it's undersized and doesn't meet the code. Getting the gas company to consult and advise up front might eliminate any surprises later.

Just some items to consider . . .


Sorry to go on . . . but I just saw mention of your generator -- lots of generators REQUIRE 11" - 14" w.c. inlet pressure at their burner manifold even for natural gas. Another reason to see what the delivery pressure is and let the gas company know that you likely need a higher delivery pressure. The addition of a generator usually results in a larger meter too so they'll want to know the details of your total connected load. They'll usually send someone out to consult with you at no charge.
 
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   / Natural Gas Pipe Sizing question #12  
The tables and explanation that ponytug provided in the "cheat sheet" are exactly what you need. But you still need to verify the delivery pressure. If you find out that the delivery pressure is 2# or something more than "low pressure", you'll need different tables. If you decide to use CSST anywhere in the system, there are separate tables for that too.

OK. Done. Just want to emphasize that I wouldn't ASSUME anything about what they're going to deliver, where they will put the meter, or how involved they want to be in the sizing and inspection.
 
   / Natural Gas Pipe Sizing question #13  
I have propane so a little different. I have a regulator on my tank providing 2# psi on the run to the house. At the house I have 2 regulators, one for the house to drop the pressure and a separate one for the generator. They are within a couple feet of each other. The pipe from the regulator to the generator is 1-1/4" and about 6' long. The piping in the house is 1/2" CSST and all appliances on is 172k btus (pipe sizing doesn't meet the charts but that's a story for another time) I've had the gas company check pressures and delivery rates and it all works properly.
 
   / Natural Gas Pipe Sizing question #14  
I have propane so a little different. I have a regulator on my tank providing 2# psi on the run to the house. At the house I have 2 regulators, one for the house to drop the pressure and a separate one for the generator. They are within a couple feet of each other. The pipe from the regulator to the generator is 1-1/4" and about 6' long. The piping in the house is 1/2" CSST and all appliances on is 172k btus (pipe sizing doesn't meet the charts but that's a story for another time) I've had the gas company check pressures and delivery rates and it all works properly.

Propane is a different animal entirely and wouldn't use the same tables. Besides having 2# delivery to the house piping, you're also pushing a gas with 2500 BTU per cubic foot as opposed to natural gas at 1000 BTU per cubic foot. Propane piping will always be quite a bit smaller based on the charts.

The only downside to this is when a person finally has a chance to convert to natural gas from propane, they sometimes find that their house lines are too small or marginal. I'm on propane too. Wish natural gas was available.
 
   / Natural Gas Pipe Sizing question #15  
I have propane so a little different. I have a regulator on my tank providing 2# psi on the run to the house. At the house I have 2 regulators, one for the house to drop the pressure and a separate one for the generator. They are within a couple feet of each other. The pipe from the regulator to the generator is 1-1/4" and about 6' long. The piping in the house is 1/2" CSST and all appliances on is 172k btus (pipe sizing doesn't meet the charts but that's a story for another time) I've had the gas company check pressures and delivery rates and it all works properly.

Also, to your point, the tables are pretty conservative. If you run the equations or use the various formulas, you can usually get by with a smaller pipe but you'll take a larger pressure drop. That's why so many systems that are undersized still work ok. If you take a 2" drop instead of the recommended 0.5" pressure drop, you can pass much more gas and often still get to the furnace or water heater that only needs 4-5" w.c. at the burner control valve.

The old Lennox pulse furnaces, for example, would throw fits if you did that though. Some equipment requires higher inputs and have very tight variance in their input pressure settings. Recently, stand-by generators have been the biggest challenge -- mainly because they're designed for inlet pressures that exceed standard traditional delivery pressures and people install them on EXISTING systems that weren't sized for the additional load. Often the generator load matches all the other equipment combined. And no matter how big a pipe you run, you can't get 11" w.c. or more to the generator if you're starting out with only 7" w.c. at the meter.
 
   / Natural Gas Pipe Sizing question #16  
Local gas company offers two meters options for home owners. One is an "inches" meter which is a white face with black letters/numbers and delivers gas at 7-10" WC. The other is a PSI meter red faced white letters and delivers 2 PSI gas. If you use a PSI meter you will likely need a secondary regulator to drop the line pressure for the appliance demand for inches of water column. I sized and executed a gas install using a 2 PSI meter thinking at the time I would add a whole house generator. I had to add a secondary reducer for the tankless water heater. It contained a warning in the instructions against using PSI input and voiding the warranty...
 
   / Natural Gas Pipe Sizing question #17  
The short answer is that there is no short answer.
First step is to determine the total BTU load on the entire piping system. Then lay it out and size the pipe according to the load. The btu delivery will vary with the length and number of fittings in the run.
Having said that, there is no imaginable way that a 3/4” pipe could not supply a BBQ in any practical installation. Could be a different story it you tee other appliances into the line.
One way to minimize pipe size on a long run is to use a higher pressure and a regulator at the load, pipe sizing charts always specify the pressure.
 
   / Natural Gas Pipe Sizing question #18  
This is been kind of an interesting/informative read. Many years ago I spent time on the oil patch and most of the wells were pumped with Ajax engines fueled but the fields own gas which we got call in to work on. This natural gas of course had no smell so we "fired" the lines before we worked on them. All in fun.
 
   / Natural Gas Pipe Sizing question
  • Thread Starter
#19  
Propane is a different animal entirely and wouldn't use the same tables. Besides having 2# delivery to the house piping, you're also pushing a gas with 2500 BTU per cubic foot as opposed to natural gas at 1000 BTU per cubic foot. Propane piping will always be quite a bit smaller based on the charts.

The only downside to this is when a person finally has a chance to convert to natural gas from propane, they sometimes find that their house lines are too small or marginal. I'm on propane too. Wish natural gas was available.
Thank you for explaining this. I didn't realize that there was this big of a difference between Propane and Natural gas.
 
   / Natural Gas Pipe Sizing question
  • Thread Starter
#20  
You really need to check with the local gas company to be sure you know what their delivery pressure is. You might even want to get one of their servicepeople or service supervisors to take a look at a sketch of your house piping and size it for you.

As mentioned above, 7" w.c. is a typical delivery pressure, BUT it's also VERY common for the gas company to deliver 2# (2 pounds) of pressure when the house piping will be run with CSST (Corrugated Stainless Steel Tubing). (That's the yellow tubing you referred to.) The reason for this is that CSST is measured OD instead of ID, it's expensive, the fittings are expensive, and the corrugations add some restriction. So in order to be able to run a SMALLER size in CSST (as opposed to black iron pipe), the delivery pressure is increased. Lots of new subdivisions are entirely 2# (PSIG) delivery now for this reason.

Also, you mentioned that "manifold" in the attic. If you're talking about the actual manifold where you'll run all your CSST branch lines to feed from, you're going to want to put that someplace more accessible. Otherwise a residential piping system wouldn't really have a "manifold". You have a main line and then branch off of that with drops (tees) as needed.

The installation requirements for CSST are defined in the manufacturers installation instructions in detail. The National Fuel Gas Code, NFPA-54 also has requirements for every material.
With CSST you have to install protective strike-plates where it penetrates framing, etc. You need to clearly understand both and be sure you know what pressure your gas company is going to deliver before you'll know how to size it. Most everywhere you have to be "certified" to run CSST. What "certified" means varies by locale.

If you're just wanting to pipe with black iron, you might be able to do the work. Here where I'm at the gas company would just inspect visually (before it's covered) and do a final pressure check. You wouldn't even need a plumber if you're doing it on your own home. This varies by locale and gas company too.

Find out what they plan to deliver. If it's 7" w.c., you'll be surprised how much pressure drop a 60' run of 1/2" pipe will take. The entire system is supposed to be sized so that you reach each appliance with only 0.5" w.c. pressure drop. That's not 0.5" drop for each branch or pipe segment -- that's total from the meter to the farthest appliance. That's by the book.

These sizing tables are readily available -- just be sure you're looking at the heading on the table and it reflects the correct delivery pressure, pressure drop, specific gravity for natural gas, and pipe material.

Sounds like there's no question that you can install the pipe. But the last thing you want is for the visual or final inspection to turn you down because it's undersized and doesn't meet the code. Getting the gas company to consult and advise up front might eliminate any surprises later.

Just some items to consider . . .


Sorry to go on . . . but I just saw mention of your generator -- lots of generators REQUIRE 11" - 14" w.c. inlet pressure at their burner manifold even for natural gas. Another reason to see what the delivery pressure is and let the gas company know that you likely need a higher delivery pressure. The addition of a generator usually results in a larger meter too so they'll want to know the details of your total connected load. They'll usually send someone out to consult with you at no charge.
Thank you, this helps a lot. As of right now, I do not have Natural Gas to my house. It's in the ground near my house, but I'm a year, or maybe even two years away from digging the trench for them to install it.

The manifold is something that I see in new construction all the time with the yellow coated gas lines. I assumed something similar would be done with black iron pipe, but now I'm thinking that I've never actually seen a manifold for black iron pipe, just T's as it works it's way through the house.

According to Lowes, my BBQ puts out 32,000 BTU's They have some that go as high as 52,000 BTU's, but I'm not buying a new one right away, but if a sale comes along, who knows.

The cost of going with 3/4 pipe instead of half inch is about 25% more money, but not so much overall that it's prohibitive. From what I'm reading, I think that I should be fine installing the 3/4 inch pipe now and in a year or two, figuring out the rest of the system requirements.

There will be nothing else that comes off of this line, I just need to get it across the living room attc, out to the porch, before I lose access to the rafters. There isn't going to be a crawl space over my porch, so the only way to get into there will be by removing my cedar on the ceiling. I'll take pictures for the gas company to look at if they need to, but if they force the issue, I'll just abandon the pipe up there and stick with propane.

None of this will be in the ground. It will run though my attic, and down through my walls.

Thank you, I feel a lot better about this now.
 
 
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