Yes, you can. Ductile Iron pipe and fittings can be direct tapped for air release valves, sampling ports, service connections, etc. You do want to ensure that there is adequate thread engagement to provide both strength and a leak-free seal. Testing has shown that, with the use of a good thread sealant, as little as one full thread engagement will provide a leak-free tap. Following the conservative nature of our industry, we recommend that you choose at least two full threads of engagement.

The limiting factor in achieving adequate thread engagement for a given metal thickness is the relative curvature of the parent body as the size of the tap increases. There are tables in AWWA/ANSI C151/A21.51 which show the maximum size of tap that can be used on a given size of pipe, and thickness to achieve 2, 3, or 4 thread engagement.

Also, you can order fittings with a boss cast at the location of the desired tap. The flat surface of the boss, along with the increased metal thickness, provides for multiple thread engagement of tap sizes larger than could be accommodated on the curved surface of the fitting.