Discovered gas leak at my 70 year old house seeping out from under the edge of patio. Turned off gas, cut out concrete, & dug out 15 ft (3 ft past patio ) of 1” black iron pipe to a collar connection in very good condition.

But there were (5) 1/16” electrolysis holes in the old 1” black iron pipe that was under the concrete really up close to the house.

I replaced everything with black iron pieces except for ( 1 union & 3 galvanized steel collars. Live in small town & lumberyard was out of black iron union & collars.

Then tested for gas leaks with soppy water. No bubbles so back filled the trench. Then discover videos on internet that suggest you shouldn’t mix the two types of piping.

Did I do bad by mixing the black iron pipe with the galvanized union & collars. Do you suggest I re-dig it back out & replace galvanized connections with black iron connections ?

  • "dig it back out & ..." what??? Don't leave us hanging! Please edit your question to finish your thought.
    – FreeMan
    Commented Jan 17, 2023 at 15:46
  • Whew! Thanks for finishing your thought. :)
    – FreeMan
    Commented Jan 18, 2023 at 15:20

1 Answer 1


There's no problem mixing & matching plain steel pipe ("black iron"), and galvanized steel pipe. However, steel pipe of any description should not be placed in the ground or embedded in concrete, unless special waterproofing materials are applied to it.

  • 1
    Yup, there is special pipe for buried steel natural gas lines. It has a green coating (colloquially called "green-dip" where I live). Fittings (whether black or galv.) are supposed to be protected with 20 mils. of gas pipe wrap tape. Commented Jan 18, 2023 at 1:41
  • Freeman, Kreemoweet & Jimmy Fix-it, thank you guys so much for you assistance. Another ( BAD ) for me, as I ( DID NOT ) use (water proof tape) or ( green dip ) pipe. I’m 70 years old & it’s hard for a OLD DOG to learn new tricks, I know better next time, Oily Tex
    – Oily Tex
    Commented Jan 18, 2023 at 18:22

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