Weil McLain 635-100-003 Air Vent

The Weil-McLain 635-100-003 Automatic Air Vent is a critical component for maintaining hydronic system efficiency by ensuring the continuous removal of trapped air. Designed for high-performance residential and commercial boilers, this #400 series air vent features a 1/2" NPT connection and is engineered to handle demanding operating conditions. With a maximum pressure rating of 150 PSI and a maximum temperature threshold of 240°F, this brass automatic air vent prevents air-bound radiators and reduces the risk of pump cavitation and system corrosion. The hydroscopic cap design allows for reliable venting while preventing leakage, making it a reliable replacement air vent for Weil-McLain boilers. Professional installers utilize this high-temp hydronic air vent to optimize heat transfer and ensure silent operation within the heating loop. Its robust construction ensures long-term performance in closed-loop systems subject to thermal expansion and variable flow rates.

• High-Pressure Tolerance: Rated for up to 150 PSI, making it suitable for high-head circulating systems.
• High-Temperature Durability: Sustains operation in systems reaching 240°F, exceeding standard residential requirements.
• Automatic Purging: Eliminates the need for manual bleeding by continuously venting air during system operation.
• Corrosion Resistance: Heavy-duty brass body provides durability against aggressive system water chemistry.
• Universal 1/2" NPT Connection: Standard sizing ensures compatibility with a wide range of boiler manifolds and air separators.

How do you troubleshoot a leaking automatic air vent?
If the 635-100-003 begins to weep, check for debris buildup in the valve seat. For system startup, the small black cap should be loosened one full turn to allow air to escape; tightening it fully will manually seal the vent.

Can this vent be installed in any orientation?
No, for the float mechanism to operate correctly and prevent water bypass, the vent must be installed in a vertical, upright position at the highest points of the boiler or piping run.

Is this part compatible with glycol-based systems?
Yes, this air vent is designed to function in hydronic systems utilizing standard antifreeze concentrations, provided the temperature and pressure remain within the 240°F and 150 PSI limits.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.