Drill and tap two ¼” NPT (pipe threaded) holes in one of the 2″ steel pipe caps as shown in Figure A. (Note that a hole for a ¼” NPT thread is a much different size than for a ¼”-diameter bolt. You need a ¼” NPT tap and the appropriate 7/16″ drill bit.) In one hole, screw in the NPT-to-barbed fitting connector; in the other hole, screw in the pressure relief valve, applying pipe compound to the threads of both.

Next, install the sight glass. The sight glass allows you to see that there is water inside the steam generator. To install, drill a hole in the side of the iron nipple using the drill that came with the ½” NPT tap set. Drilling a hole that big in a pipe is not at all easy, so clamp the work securely, use cutting oil, and go slowly. Tap the hole with the ½” NPT tap. Apply pipe compound and twist
in the sight glass.