ASC Engineered Solutions 21/2 BLK MI WYE

All three openings are 2-1/2 inch FPT, so it's a full-size wye with no reducing branch. Threads are cut to ASME B1.20.1 (NPT), so it makes up with standard threaded black steel pipe and nipples. Every port being female means you thread pipe or nipples directly into the fitting on all three sides.

Black malleable iron fittings are the standard for gas piping and for wet fire sprinkler mains, both of which are closed systems where the uncoated iron isn't exposed to air. What you don't want it for is open potable water service or anything where corrosion resistance matters, since the finish is plain black with no galvanized coating. For potable water, go galvanized or copper/CPVC instead.

A tee takes the branch off at 90 degrees; a wye takes it off at an angle, so flow turns more gradually. That lower turbulence matters on drainage and on anything where you want to keep pressure drop down on the branch. On a 2-1/2 inch threaded black iron line, this wye gives you a full-size 2-1/2 inch branch, so there's no restriction at the takeoff.

The casting is ASTM A-197 malleable iron, with dimensions and pressure rating to ASME B16.3 and threads to ASME B1.20.1. Those three together are typically what a submittal on a threaded black iron fitting asks for, so it covers the spec line on most commercial drawings calling out Class 150 standard weight malleable iron.

The wye is the fitting only. You supply the threaded pipe or nipples for all three 2-1/2 inch FPT ports plus thread sealant rated for the service (gas-rated compound or PTFE tape for fuel gas). No gaskets or bolts are involved, it's a straight threaded makeup.

Order it as MPN 310067806 from ASC Engineered Solutions. It's the 2-1/2 x 2-1/2 x 2-1/2 black malleable iron wye, standard weight, all female threaded ends.