Gas line size for pool heater

JSM5

I have a 1.25" line coming off the gas meter. If we came off that line in the basement, the distance from meter to pool heater would be 123'. The manufacturer says it needs to be a 1.5" at that distance to adequately supply a 400K BTU heater. I've had a plumber say we have to run a new 1.5" line from the meter. Another is saying that we can just add the 1.5" onto the 1.25" for the distance of basement to equipment. Although that's a cheaper option, it doesn't sound right to me. Any thoughts?

ChrisJ

JSM5 said:

I have a 1.25" line coming off the gas meter. If we came off that line in the basement, the distance from meter to pool heater would be 123'. The manufacturer says it needs to be a 1.5" at that distance to adequately supply a 400K BTU heater. I've had a plumber say we have to run a new 1.5" line from the meter. Another is saying that we can just add the 1.5" onto the 1.25" for the distance of basement to equipment. Although that's a cheaper option, it doesn't sound right to me. Any thoughts?

How long will the 1.25" run be?

For example, 10 feet of 1.25" (assuming no elbows) can easily carry over 1000 CFH, or approximately 1,000,000 btu/h. Each elbow will add a few feet to the overall length.


I don't know what the rest of your load is, but the second option is certainly plausible.

STEVEusaPA

It's all about pressure-flow and volume. It's not 1.5" from the street, right? I think your fine.

EBEBRATT-Ed

Run a new line from the meter to the pool heater. 400k is a large load and it all comes on at once.

Adding the pool heater to the existing 1.25 pipe with the existing load is no good.

JUGHNE

Usually easier teeing in at a meter than the middle of a basement run.

Gordy

First step. What size is the meter? Is it big enough to supply the loads to the home, and the pool heater?

EBEBRATT-Ed

meter is likely too small. The gas utility will usually upgrade for free

Gordy

I know, but do the installers?

EBEBRATT-Ed

@Gordy, your right. I am used to Massachusetts overregulation. When we add something as large as a pool heater we have to get a "letter of availability" from the gas co stating that they can supply the cfh and pressure needed by the equipment.

The inspector is "supposed" to ask for this as we have to list the existing appliances and load and the added load. But your right not all location are as strict as The Peoples Republic of Massachusetts!!

Leonard

Sounds like they're concerned with everyone here switching to nat gas from oil, so some gas co's might have trouble supply gas.

Pool heater sounds like a non-issue since unlikley to run it in winter when wide spread winter heating makes gas co's have to supplement nat gas pipeline supply with propane

JUGHNE

It seem every gas company would want a pool heater on every meter.
For us out here it is center pivot irrigation pumping.

Gordy

Leonard said:

Sounds like they're concerned with everyone here switching to nat gas from oil, so some gas co's might have trouble supply gas.

Pool heater sounds like a non-issue since unlikley to run it in winter when wide spread winter heating makes gas co's have to supplement nat gas pipeline supply with propane

It’s a 400k pool heater...... most meters are standard 250......

Throw in gas dryer, stove, grill, water heater those get used in the summer.

ChrisJ

Except, once again, 1.25" at 10 feet will handle over 1,000,000 btu/h with only 0.5" drop.

Saying "it won't work" without knowing how long that pipe is (including elbows) seems ridiculous to me.

The meter size is a totally separate subject.

Zman

ChrisJ said:

Except, once again, 1.25" at 10 feet will handle over 1,000,000 btu/h with only 0.5" drop.

Saying "it won't work" without knowing how long that pipe is (including elbows) seems ridiculous to me.

The meter size is a totally separate subject.

The original post says 123' (plus fittings I assume).
1.25" will not work, 1.5" is a little close.
It might be worth considering running it from the meter at 2 PSI. You could use 1" poly and bury it.

ChrisJ

Zman said:

ChrisJ said:

Except, once again, 1.25" at 10 feet will handle over 1,000,000 btu/h with only 0.5" drop.

Saying "it won't work" without knowing how long that pipe is (including elbows) seems ridiculous to me.

The meter size is a totally separate subject.

The original post says 123' (plus fittings I assume).
1.25" will not work, 1.5" is a little close.
It might be worth considering running it from the meter at 2 PSI. You could use 1" poly and bury it.

The 123 feet is to be 1.5".
He's asking about tapping into a 1.25 inside the house, I assume a short distance from the meter.

ratio

It will almost always "work", in that gas will come out close enough to the right place & close enough to the right pressure to burn. In fact, it can be undersized all the way down until the inlet pressure barely meets the nameplate minimum input pressure, & this will work fine, as long as the pressure doesn't vary significantly. Where we run into difficulties is when the pressure is variable due to other loads coming in and out, or even supply pressure (although that's not a common issue around here).

Pressure regulators are not ideal devices, the only way they know to feed gas is if the pressure drops below the setpoint. To get more flow out of them the pressure has to sag further. So, as appliances use more and less gas, the pressure fluctuates; this is amplified by the pressure drop of long small piping, & makes it hard (impossible?) to dial in the combustion across the range of inlet pressures if the variance is too large. If you dial it in when the pressure is highest, you'll be underfired when the pressure drops & vice versa. Split the difference? Set it up when the most common loads are firing?

It'll probably work ok if you tap the 1-¼" close to the meter. If you tap it on the other side of the basement, tell us how long the 1-¼" is & how many fittings are in it. If you're at 100' equivalent length at the point you want to tap it, probably won't work out so good.

Leonard

400K BTU..... Even if meter can take it , likely have to change safty flow orfice at meter to a larger size to allow the flow. Typical house furnace might only be 70k-150k BTU and orifice is likely sized to near your max load in case of a pipe break.

Run into same issue when adding 240K BTU load of a large 15kw gen, (Onan 15JC)