Xylem 74 Steam Unit Heater Air Vent Valve 1/2" x 3/4" 35 PSI (401429)

The Xylem Hoffman Specialty Model 74 (MPN 401429) is a float-type thermostatic steam unit heater air vent valve designed to automatically purge trapped air from steam heating systems. By venting air efficiently, this valve ensures proper steam distribution throughout unit heaters, improving heat transfer and overall system performance.

Key Features:

• Float-type thermostatic vent — automatically opens to release air and closes when steam is present
• Single non-adjustable port — simple, reliable design with no adjustments needed
• 1/2" NPT female x 3/4" NPT male straight shank connections for straightforward installation
• Maximum operating pressure: 35 PSIG (2.4 bar) — rated as the maximum drop-away pressure against which the vent can open
• Temperature range: 140°F – 240°F
• Steel body construction for durability in demanding steam applications
• Non-vacuum design — suitable for standard steam unit heater systems

Installation Notes:

• Install 6 to 10 inches (150–250 mm) above the horizontal return
• Install 18 inches (450 mm) above the boiler water line

This valve is also sold under the updated part number 401429 (supersedes legacy model number 74). It is a Hoffman Specialty product, a brand under Xylem Inc., and is also distributed under the Bell & Gossett brand. Ideal for residential and commercial steam heating systems requiring reliable automatic air venting at unit heaters.