Gas pipe size for pool heater?


New member
Apr 20, 2018
Orange County, CA
Hi guys,

The previous owner of my home had a natural gas heater for his jacuzzi and also a natural gas grill that were each served by their own 3/4" gas pipe. He removed both of these items and capped off the two 3/4" gas pipes which are located next to my pool pump / filter. My understanding is that even a "small" pool heater (e.g. 260K BTU) needs at least 1" or 1.25" gas pipes and that a 400K BTU heater likely needs 1.5" pipes.

Can I somehow combine the two 3/4" pipes (Y-connector?) to create a larger 1.5" pipe and get the required gas flow for a pool heater or am I looking at an expensive new pipe-laying under my home? Apologies if this is a dumb question!




TFP Expert
In The Industry
Jul 6, 2011
No. You need a larger pipe from the source to the equipment. Find a qualified gas person to check things out and provide you a solution.


Gold Supporter
TFP Guide
Jun 7, 2017
Damascus, MD
You can use a smaller pipe if the pressure is increased. This is how my 400k NG heater gas line was run. The gas company installed a high pressure outlet on my meter and they ran it from there. I think it is only 3/4". Ask your gas plumber!


Gold Supporter
Jun 3, 2015
Reno, NV
My gas supplier did something to mine. I've been running a 1" line about 35' for a 400k for 17 years and two heaters and no problems.


Gold Supporter
LifeTime Supporter
Aug 6, 2010
Durham, NC
The previous owner of our house (aka Beauzeaux, who amazingly was a pool contractor) installed a 75 foot run of 3/4" gas pipe from the meter around the outside of the house to the pool heater.................using PVC pipe!

Using a published table, the HVAC contractor I engaged to replace the gas line to the pool heater determined that 3/4" would be too small for that long a run. There would be too much pressure drop. The solution was to upgrade to a "2 pound" system. The gas company installed a different meter which outputs gas at 2 PSI. The piping from the meter into the house was still 3/4", but there is a regulator at each appliance (furnace, stove, pool heater) to drop the pressure. The project took several days and lots of $$.

After all that, when I fired up the pool heater, I discovered that because of the undersized (3/4") piping that Beauzeaux used, and the resulting low gas pressure, the burners in the heater had been running "cool" with lots of moisture in the flames. Because of the moisture, the core of the heater was entirely rusted out. I ended up junking the heater and replacing it with a heat pump. (The core had also dumped copper into the water, which turned bright green the first time I shocked the pool.)

If you can upgrade your house to a "2 pound" system, you should be able to use one of the existing 3/4" pipes. As recommended above, do consult with a qualified plumber or HVAC contractor.


Well-known member
Jun 8, 2014
Rogers, AR
I am currently going through the gas line issue. My house only has 250k coming in and my heater is 400k. I need 650k to run my heater and the things in my home. The max they can bring in on a regular meter in my area is 600k. The plumber (to the tune of $2,000) installed all the needed things this week and tomorrow the gas company is coming to change out my meter and regulator. I am going to be overclocked at 850k. The gas company told me not to turn my heater on until the work is completed because I could blow out my line.