ASC Engineered Solutions 21/2X11/4 BLK MI REDUCER

It joins 2-1/2 inch pipe down to 1-1/4 inch, and both ends are female pipe thread (FPT). So you thread it onto male-threaded pipe or nipples on both sides, no welding or grooving involved. Threads are cut to ASME B1.20.1 (NPT), which is the standard taper thread on black iron pipe systems.

No. Black malleable iron is for non-potable service: fire sprinkler, natural gas, compressed air, steam, and closed-loop hydronic heating. The black finish is a mill/oil coating with no corrosion protection against fresh water, so on domestic water you want galvanized, copper, or CPVC instead.

A reducing coupling has female threads on both ends, so both pipes thread into it and the reduction happens inside the fitting body. A bushing is male on the large end and female on the small end, and it screws into an existing female port such as a tee or valve. This ASC fitting is the female-female type at 2-1/2 x 1-1/4, so use it mid-run between two male-threaded pipe ends; use a bushing when you are reducing out of a fitting you already have in place.

This one is standard weight (STD), rated per ASME B16.3, which is the 150 class malleable iron standard used on ordinary fire sprinkler, gas and air piping. If your drawing calls for extra heavy (300 class) at that point, this is not the fitting; you need the 300 class equivalent.

Order ASC Engineered Solutions model 310090402. The fitting weighs 2.09 lbs, which matters if you are hanging a run of them or building a shipment quantity for a job.

Yes, the NPT threads to ASME B1.20.1 are a tapered thread and seal on the thread flanks, so they need a sealant. Use PTFE tape or pipe joint compound rated for the service you are running, and confirm the sealant is listed for fire sprinkler or gas if that is the application.