Originally Posted by Hardway
The hell they will seal, pipe dope is need to seal the pipe tthreads on gas, water and air! The threads are tapered so they tighten up. If pipe dope was just to lube the threads, the cutting oil would do to seal the joint!
Long long before any of the thread sealing compounds were commonly known. I was putting pipe together with only dope. Dope that still to this day has no sealing ability, and those joints then as now, don't leak.
Tapered threads seal themselves. The dope is only a lubricant. Thee's more then a million pipe joints that have a lubricating dope on them, not a sealing dope. And those joints don't leak.
If it was the dope that seals the joint. Then tapered threads wouldn't be needed. You would just run the pip in until it hit the other pipe and tighten it as you would a nut and bolt.