Find and fix black pipe leaks

[Frank The Plumber]

I generally do not like the types of pipe dopes that harden, I have the best result with a pliable dope that has a teflon base and can absorb small differences in pipe temperature. I also like the rectorseal because it is water safe, this is important because you will always tend to grab what's close or easy, you really don't want an employee using a sealant that is going to get someone sick. Generally no more than about a 30 degree backout will be tolerated by rectorseal. Most DIY's use a steel coupling not a malleable one. If you took a micro meter and measured the exterior of a steel coupling, installed it, removed it and re mic'ed it, you would notice that the steel coupling has stretched to a larger diameter and fluted, it has no return stretch or "malleability", the cast fittings have a special design and materials that allow them to form to the thread and return to shape around it. They do not flute. Non malleable fittings have zero back out tolerance.

 

[csargents1546]

When I did my air lines in my old house, I used rectorseal pipe dope and no tape. I held 150psi at the compressor and 110 in the rest of the lines with no leaks. The key was I threaded all my own pipe, bought a used ridgid pipe hand threader. Pipe dope is a much more forgiving product than tape.

 

[Brust]

How long should a line hold pressure for? I pressurized mine to 5 psi and it bleeds down overnight. I'd think that you want it to hold indefinitely, but I also cant tell if the upstream valve is leaking by. The soap test reveals nothing- no bubbles, nothing.