Last night while checking on one of the buildings I manage, I noticed
a pinhole leak coming from a 2" steel pipe that enters the side of the
boiler. The leak is not at the boiler, but at the top of the pipe
( it's a horizontal pipe). Fortunately it is above the water line. I
assume its probably because of corrosion, but in any event I shut down
the boiler and went to a nearby hardware store and purchased 2 part
epoxy, and applied it to the pinhole. Waited about an hour, fired up
the boiler and let it get to full steam at about 3PSI. I saw no leaks
after sitting there about an hour monitoring the situation. I'm
wondering how long it will hold. But one thing I noticed is the epoxy
dried as hard as steel.

How are these pinhole leaks usually repaired? I heard of JBweld, but
you need to wait a while until it sets, plus its rated to only 200-250
degrees. The stuff I used is rated to 300 degrees.