Wanting 400kbtu/hr heater--what upgrades are needed upstream in gas line?


Active member
Apr 4, 2015
Western, WA
Hello TFP,
I've used a (well used/mature) 250kbtu/hr Laars heater on our 18'x48" AGP last year. Today we just installed a new pool--a 26'x52" AGP. It's huge! My gas piping it set up to handle the 250kbtu/hr heater (1" gas piping most of the way from the meter. But per Raypak's installing specs, I would need larger piping- at least 1-1/4 for the 400kbtu/hr heater. Looking at Home Depot yesterday, the only thing larger than 1" black pipe is galvanized.
A. Is galvanized okay for low pressure natural gas service? Or do I just need to find 1-1/4 or 1-1/2 black pipe from somewhere else?
B. I talked the the gas company, and they are willing to install a larger capacity meter for free. They are asking if I want an increased meter output pressure. This I don't know--what are your thoughts and how would higher pressure impact the rest of my gas using appliances inside my home? Is there any benefit of increasing gas pressure to the pool heater?
C. With a 14k gallon pool, will I really notice that much speed difference in heating the water with a 400kbtu/hr heater vs. sticking with a 250kbtu/hr heater? I like the idea of the larger size, but I'm starting to get worn out from all this work!
D. Right now my 1" gas line for the heater T-'s into the gas line under our home that feeds multiple appliances. I'd like to have a T coming right off the meter with a dedicated line from that T going to the heater. I'm wondering if I can run this gas line externally along the side of the house to the heater? Paint it for rust prevention?

Thanks for all input!


TFP Expert
Apr 29, 2016
Quaker Hill, CT
They definitely make black iron pipe bigger than 1". You will need to look for it at a plumbing supply house or another hardware store.

A) Galvanized might be ok you will need to check with your local building inspector as what pipe they are ok with.
B) Upping output pressure of the meter will increase the BTU output of a pipe. Upping the pressure can definitely affect your other appliances in a negative way if not done correctly. A local licensed professional is your best bet for that info.
C) 250k will heat your new pool just fine. 400k will heat it about 25% faster.
D) This need to be answered by your local building inspector / local licensed contractor. Local codes will dictate if that is ok in your area.


TFP Expert
In The Industry
Jul 6, 2011
See your local codes as to what they require for gas line type. Here in FL it's all galvanized pipe and some copper for propane.

As for the increased out put of a new meter, you would need to make sure your appliances can handle it and the regulator that they have on them will handle it.

Coming off the meter directly to the heater is a good idea and recommended if possible. No need to paint. Check with local codes to see what they require for an external line. Maybe go the route of the PE type line and put it underground.