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Discussion Starter · #1 ·
I am installing a 400,000 BTU water heater for swimming pool. Need to run a natural gas line about 20 ft from my water heater. I'm working with town to get permit and have plumbing make the connection to the water heater after I have installed the line. I'm planning to a simple straight 20' STR11 pipe underground connected to 2 risers to feed the pool heater. No plans to ever extend the line for anything else. I can't get a clear answer from the gas co on what size pipe I need to use. The 1st pipe sizing chart I saw says to use 1-1/4" pipe for natural gas for 20' distance in order to provide 441 BTU. But this is for the table with Gas Pressure of 0.5 psi or Less and a Pressure Drop of 0.5"WC . There are other tables. How do I know what gas pressure and pressure drop is, so I use the right table. I asked the gas company, but they couldn't didn't know how to answer.
 

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I am installing a 400,000 BTU water heater for swimming pool. Need to run a natural gas line about 20 ft from my water heater. I'm working with town to get permit and have plumbing make the connection to the water heater after I have installed the line. I'm planning to a simple straight 20' STR11 pipe underground connected to 2 risers to feed the pool heater. No plans to ever extend the line for anything else. I can't get a clear answer from the gas co on what size pipe I need to use. The 1st pipe sizing chart I saw says to use 1-1/4" pipe for natural gas for 20' distance in order to provide 441 BTU. But this is for the table with Gas Pressure of 0.5 psi or Less and a Pressure Drop of 0.5"WC . There are other tables. How do I know what gas pressure and pressure drop is, so I use the right table. I asked the gas company, but they couldn't didn't know how to answer.
How close are you connecting to the gas meter? At that size, you'd have to connect within 6", or upsize the line to the hot water heater.

Where do you live. I only have tables for Ontario, but they will be close for other jurisdictions. If your gas connection is really old, then your supply it could be "less then 7"wc". Newer supplies are now typically 7-14"wc. That's a question that your gas supplier can answer. (they won't be willing to do sizing.) You can also measure it if you have a manometer.

Cheers!
 

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Discussion Starter · #3 ·
So I'll plan to install the line within 6" if that's what is generally required. The gas company said they'll upgrade the gas meter since I'll require more supply. I live in Southlake TX (near ft. Worth).
 

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So I'll plan to install the line within 6" if that's what is generally required. The gas company said they'll upgrade the gas meter since I'll require more supply. I live in Southlake TX (near ft. Worth).
You should be good with 1".

At 7-14"wc you're good to 50ft. At less the 7"wc your good to 20ft. (422kbtu)

(of course, like I said that's using Ontario code tables. It should be in the ball park for you.)

Cheers!
 

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Discussion Starter · #6 ·
Another question. I ordered my parts (SDR11 pipe and risers) for the new gas line. Does the new gas line just Tee into the existing one going into the house? Do you add a manifold??

I had a plumber come out to quote the job. It was $4k for the job so doing much of it myself. He said he'd add two regulators. One at the meter and one at the pool heater. The one at the meter brings the medium pressure (from the new meter that the gas co will put in) down to what it needs to be at for the heater. Then another regulator at the pool heater? Why would 2 be needed? Wouldn't one at the the meter be enough to bring the pressure down and supply adequate to supply the 400k BTU required by the pool heater?
 
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