Drill and tap two 1/4″ NPT (pipe threads) holes in one of the 2″ steel pipe caps as shown in Figure A. (Note that 1/4″ NPT threaded holes are a significantly different size than 1/4″ diameter bolt holes. You will need a 1/4″ NPT tap and an appropriate 7/16″ drill bit. Screw an NPT-to-barb fitting connector into one hole. Screw a pressure relief valve into the other hole and apply pipe compound to both threads.
Next, install the sight glass. The sight glass allows you to see if there is water inside the steam generator. To install, use the drill that comes with the 1/2” NPT tap set to drill a hole in the side of the iron nipple. It is never easy to drill such a large hole in a pipe, so clamp the workpiece securely and work slowly using cutting oil. Drill the hole with the 1/2” NPT tap. Apply pipe compound and screw in.
In the peephole.
