Increasing pipe size AFTER gas meter?

m_spline

Hello All.

I want to install a 330k BTU pool heater. The heater will be 140' away from my gas meter. According to my gas utility, the pressure is 6" wc, specific gravity of 0.60 and they size on a pressure drop of 0.5" wc.

When doing these calculations, I find that I need a 1.5" pipe running from my gas meter to my pool heater.

I contacted the gas company, I had them create a quote to resize my meter because I only have a 250k BTU meter with a 1" pipe coming out the top. I filled out all the proper paperwork, explained what I was doing and what I needed, and they sent me a quote, with no specific information, just explaining it as a "meter upgrade." After some confusion on email/text, I spoke with the "engineer," on the phone. It took him quite a long time to understand that all I wanted to know was what size pipe was coming out of the output (residential) side of the new meter. He kept explaining that the residential side of the meter has nothing to do with them... Finally he understood and told me it was still a one inch output.

I explained to him, again, that I required a 1.5" output. He told me that didn't matter, that I could put a fitting on to increase the pipe size to 1.5" on the residential side.

Now I'm no expert (I am a mechanical engineer, but I've done very little with pipe flow), and I think I know enough to know that placing a 1.5" pipe after a 1" pipe will reduce my volume to only the 1" size and drop my pressure as well. He told me it won't and it'll be fine.

Is he right or wrong? I'm not going to spend the money on a contractor and the upgrade if I can't sufficiently supply my heater with fuel.

Thank you in advance.

Larry Weingarten

Hello, It seems that increasing pipe size will cut friction loss/pressure drop through that 140' of pipe and give you a higher delivered pressure. What is the gas inlet size on the equipment? Another option to consider would be to go with a smaller pool heater and keep a cover on the pool to cut heat loss through evaporation.

Yours, Larry

mattmia2

He is right because gas is compressible.

ChrisJ

mattmia2 said:

He is right because gas is compressible.

When running a certain volume of gas through a pipe and changing sizes, is anything compressed or expanded?

I.E. going from 1.5" to 1" and back to 1.5" and so on. I don't think the pressure increases in the smaller pipe?


@m_spline As Larry said you'll be fine.
As long as the pressure drop through the meter isn't excessive and you size your pipe to get the amount to the appliance needed with minimal drop it'll be ok. The small section of 1" pipe will not create enough of a pressure drop to matter.

m_spline

Larry,

Thank you for the reply. The gas inlet is 3/4".

mattmia2

ChrisJ said:

mattmia2 said:

He is right because gas is compressible.

When running a certain volume of gas through a pipe and changing sizes, is anything compressed or expanded?

I.E. going from 1.5" to 1" and back to 1.5" and so on. I don't think the pressure increases in the smaller pipe?

The pressure decreases and the volume increases in the larger pipe so the pressure is less in the larger pipe. With something virtually non compressible like a liquid the small section of pipe would act as an orifice essentially setting the flow through the larger pipe, the friction losses in the large pipe wold be negligible compared to the small pipe unless the larger pipe was very long or the very close in size to the smaller pipe. The flow doesn't increase in the larger pipe with a non compressible fluid.

m_spline

Thank you all for your comments and help, it is much appreciated and makes me feel much better to move forward with the project!

JUGHNE

That short "bottleneck" does not seem to matter, the friction of pipe and fittings is what would drop the pressure.

I have a school that had a 1.4 million boiler that had 1 1/2" meter feeding 3" pipe going inside. Of course it was the bigger meter, but still had only 1 1/2" spuds.

jacobsond

Just a little info. May be irrelevant but I found interesting. I was on a fire department tour with a local natural gas company. It was on their pipeline going to a flour plant and a big grain drier. I believe it was 600lbs pressure going into a regulator output was 90lbs. The 90lbs ran about 2 miles. The pipe size on the regulator was 1.5 inch. Pipe going down the line was 3inch I believe. All the gas going to the mill and drier through that. The little town is next on the list to get natural gas. He said that setup would have no problem with supplying a lot more. Its all about the pressure in your supply line and what you can set your regulator to from what I can tell.

Steamhead

JUGHNE said:

That short "bottleneck" does not seem to matter, the friction of pipe and fittings is what would drop the pressure.

I have a school that had a 1.4 million boiler that had 1 1/2" meter feeding 3" pipe going inside. Of course it was the bigger meter, but still had only 1 1/2" spuds.

This. The short length of pipe coming out of the meter is why this will work. The longer pipe is sized larger to minimize the pressure drop over the longer distance.

EBEBRATT-Ed

@m_spline

What the gas company told you is completely normal. They know the flow they can get through the up sized meter. 1 nipple and one reducing (in this case increasing fitting) won't matter. Just make sure the pool heaters minimum inlet pressure is met. Gas company pressure-pipe loss

JohnNY

Look at the chart below. The length of pipe has a tremendous effect on the delivery potential. The short 1" swivel or union connection on the outlet of the meter will pass all that the meter's capacity. We increase pipe diameters after the meter on the regular.

EBEBRATT-Ed

@m_spline

Make sure you allow for the pipe fittings as well as the pipe. Your getting close to the end of the 1 1/2" pipe capacity. Hate to have to bump it to 2" but with only 6" of gas pressure to start with......are you using steel pipe or plastic pipe........plastic probably has less resistance

mattmia2

If the input of the appliance is 5.5 or 5 or 4.5 min also makes a big difference here. That chart is for .3" drop instead of .5" drop. The charts also usually assume some number of fittings that are mentioned in the footnotes that frequently don't come with the chart when it is reproduced.

GW

Yes that’s a thing. The next time you’re at any restaurant or drive through, just look at the meter and piping