Running a natural gas line???

[leo raph]

I am running natural gas piping (3/4") to a pool heater outside (for a hottub). A plumber told me that I should use Black Iron on the inside and Galvanized on the outside run. But how do I join these two? I am worried that there will be a corrosive effect if the two touch.

Also, at what point do I switch between the two types? The outside wall is a 2 foot masonry wall (old house!). I know I'm supposed to use a plastic sleeve while running thru tha masonry. So should I change from black to galvanized immediately after getting to the outside?

Also, I understand that galvanized corrodes when exposed to natural gas... wouldn't it be better to use black iron outside then? and to just rust-paint it really well? My outside run is all above-ground.

Thanks,
Leo

[Richard Gillespie]

I'm not an expert or licensed. I'm retired from a Natural Gas Distribution Company and have never used any other iron pipe but black pipe for both inside or outside installations. It is my impression that galvanized pipe was to be used for water installations and black pipe for natural gas. The only other installation I've been involved with was the 2# system with copper pipe used in some homes.

I hope this helps but in all honesty, I've been retired for over 10 years and things change.

[Frank Hagan]

Here in California, they used to sell coated black iron pipe for burial use and outdoor exposure use for gas lines. See if your local store has that ... it was green in color, and had a thick coating on it ... almost like an epoxy coating (not sure what the actual material was).

They used to sell yellow PVC pipe for natural gas, but it could be buried only, and not used above ground at all. A special transition fitting has to be used to come above ground. Black iron pipe can be used, but should be wrapped (subject to local codes). There's no electrolysis between black iron pipe and galvanized pipe, but you can have galvanized flakes coming off the pipe and getting trapped in the appliance's gas valve. Home Depot and Lowes have all the fittings, etc. that you need to meet the local codes.

On Propane, it may be easier to get the local propane company to help you. Propane can use a two pressure system to help save money on longer runs. A higher pressure system might use 3/8" copper pipe from the tank to a second regulator, where it drops the pressure down to 11 - 14" water column, and then the pipe is increased in size to the 3/4 or 1" the appliance needs for the rest of the run.

You didn't say what the input BTU/hr rating of the pool heater is, but the instructions will have a chart showing how large the gas line needs to be (they should list both LP/Propane and Natural Gas). For instance, a 175,000 BTU/hr input heater running on natural gas needs a 1" gas line if it is within 1 to 100' of the meter. If you are running the line farther than 100', then the size of the gas line has to be increased to 1 1/4".

[Joe Mioux]

Wow this is a revived old thread. Black pipe is normal around here but across the river (the Mississippi) one of the greenhouses I frequent used 2" copper.

Before you do anything, contact your NG gas company for recommendations. This is one area where you do not want to skirt rules and regs. They will also tell you other important stuff like size of pipe etc.

Joe