ok to re-use gas pipe, fittings, and valves?
gblotter
| Posted in Construction Techniques on
I am re-routing a gas line in the crawl space under my house.
Is there any reason why I should not re-use the existing black pipe and galvanized pipe (and fittings) for the new gas line?
Also, is there any problem in re-using the existing ball valves for new gas appliances?
Of course I will be doing a pressure check for any leaks in the new gas line.
Replies
No problem with used gas pipe/fittings.
All gas flows thru used pipe.
Note that many jurisdictions do not allow galvanized pipe to be used for gas.
Good to know - I'll check on that.
Is that to eliminate any confusion between gas lines and water lines? Or is there a technical reason to not use galvanized pipe/fittings for a gas line?
The old gas line is a mix of both galvanized and black pipe.
Yup
While I don't know what it is, my understanding is that there is a technical reason black pipe is mandated. Perhaps the gas interacts with zinc?
The nationally-recognized codes allow galvanized to be used in gas piping.
The reason that some local jurisdictions don't allow it, or did not allow it in the past, is because of the fear that the zinc coating might flake off and cause problems with appliances.
I've heard several reasons:
1) The reason most often quoted here is that the zinc plating can flake off and clog orafices.
2) But I also heard, as a youth, that the way galvanized pipe is (or was) manufactured makes it more likely to leak. Steel pipe is made by taking a flat strip of steel and forming it into a tube. With black iron pipe the seam is welded, but with old galvanized pipe the galvanization was assumed to seal the seam -- no welding. For this reason galv pipe was more apt to have tiny leaks that would actually self-seal (to a point) when water ran through, but which could cause serious problems if the pipe was carrying gas. (And I have, on several occasions, seen old galv pipe spring leaks at the seam, so I know the seam is at least a weak spot.)
Now I suspect that current galv pipe is welded about as well as black iron pipe, but old habits/prejudices die hard.
3) I also recall hearing it claimed that galv pipe doesn't seal as well at threaded joints, for some reason.
Every time you tighten a fiting, you take a chance that you'll damage the threads. What were once 'NPT' now become threads custom molded to the piece they're mated with.
End result? It's harder to make a good joint again, with a different fitting. You end up chasing leaks and fighting the things. That's a lot of guff for a $4 fitting.
That's why plumbers rarely re-use stuff.
I've never had a problem re-using screwed fittings or pipe in 45+ years of plumbing and steam-fitting.
valves are the first thing to leak so I don't know any top plumbers that would reuse a valve. As for reusing pipe - if it's in good condition and looks like it was installed in a workmanlike manner to begin with I'd probably reuse pipe, but not fittings. One of the few cracked fittings I've ever had was one I had reused and my guess is at some time in the past it was overtightened and cracked then or was on the verge and the stress of being reused did it in.