Taco Air Scoop is designed to slow the water velocity to separate the air from solution. The unit is manufactured from cast iron and features equal threaded inlets on both sides. Top of the air scoop features a 1/8" NPT outlet (for connection of a regular air vent such as Taco 400-4) and an additional 3/4" FNPT outlet for the exoansion tank. Bottom of the air scoop has a 1/2" NPT threaded outlet, which also allows to connect a plain steel diaphragm expansion tank.