1980’s Mystery - Gas Line Size for Pool Heater

[JamesW]

I think that the line size is ok based on your measurements.

If someone says that the line is too small, ask them to give you a detailed description of why they think that it is too small.

 

[JamesW]

If you use the calculator below using the following for the 3/4” pipe:

0.824 I.D (inside diameter)

0.3 inch water column drop

3 foot length

0.6 specific gravity

You get 385 cfh capacity.

If you use the calculator below using the following for the 1-1/4” pipe:

1.380 I.D

0.2” wc drop

38 foot length (includes (4) 90s)

0.6 specific gravity

You get 389 cfh capacity.

Adding them together, you get a 0.5” w.c drop, which is acceptable.

Natural Gas - Pipe Sizing Calculator

Calculate capacities and dimensions of natural gas pipe lines.

www.engineeringtoolbox.com

Natural Gas Pipes - Low Pressure Capacities vs. Size

Sizing low pressure natural gas pipe lines - Imperial units.

www.engineeringtoolbox.com

 

[JamesW]

The pressure drop should be between about 0.5" w.c and 0.66" w.c.

Your heater specifies an inlet pressure of 6" w.c to 10" w.c.

As long as the output of the meter is at least 7" w.c, the pressure to the heater should be above the minimum of 6" w.c.

The downstream pressure after the meter/regulator is usually in the range of 7 to 11 inches Water Column.

So, as long as the meter is rated for at least 380 cfh and it outputs at least 7" w.c, you should be fine.

 

[MITBeta]

The gas meter riser from the main is high pressure, so it can be a much smaller diameter and still carry plenty of gas. Don't worry about that part of it.

 

[JamesW]

It's difficult to tell for sure what the exact outside diameter of this pipe is.

Can you measure it exactly with a caliper?

Husky 5 in. High Contrast Vernier Caliper 722H - The Home Depot

The General Tools 5 in. Fractional Scale Vernier Caliper delivers accuracy and precision when searching for inside, outside or depth measurements. It features a smooth-action thumb roller and eases repetitive

www.homedepot.com

 

[cowboycasey]

I bought a caliper thinking I would only use it once or twice.. I end up using it once a week at least if not more..

Got this one next day https://smile.amazon.com/gp/product/B07KXZDCZ2

 

[wireform]

I bought a caliper thinking I would only use it once or twice.. I end up using it once a week at least if not more..

May I ask for what, I live with them in the machine shop.

 

[cowboycasey]

all kinds of stuff.. I just build a vinyl fence on my front porch and measuring a couple things on that.. Replaced my hinges on my gates.. measured the bolts for my bridge in the front yard.. They work great for exact little measurements

 

[adambca]

Just an update, used a digital caliper and confirmed that the larger pipe is 1.66 OD so 1 1/4.

 

[JamesW]

Just an update, used a digital caliper and confirmed that the larger pipe is 1.66 OD so 1 1/4.

That should be fine for gas pipe size.

You typically have a transition from 3/4" to the larger pipe at the meter and at the heater.

As long as the 3/4" pipe is not more than 5 feet total, it's fine.

Here is what it should look like at the heater with the 1-1/4" pipe coming out of the ground and transitioning to the heater at 3/4".

There should be a shutoff valve and a drip leg that can catch debris.

The drip leg should go up and then down so that the gas has to change directions like in the picture to increase the ability of the drip leg to catch debris.

Did you find a meter data label with the CFH rating?