The Honeywell E121 is a precision-engineered automatic venting device designed for hot water heating systems, radiators, boilers, and air separators . Unlike manual bleed valves that rely on you to remember to vent the system, the E121 works autonomously. Its internal mechanism features a heat-resistant synthetic float that operates a lever in response to the water level .

• During Filling: When air is present and there is no water in the housing, the float drops, opening the valve to release air.

• During Operation: Once water flows in, the float rises and automatically closes the valve, preventing any water leakage .

This continuous process removes dissolved oxygen and trapped gases as they collect at the highest points of your system, preventing pressure imbalances and water hammer without any manual intervention .

• Maximum Operating Pressure: 10 bar (145 psi) 

• Max Media Temperature: 110°C (230°F), making it suitable for high-temperature hydronic systems 

• Materials: Features a durable brass housing and lid for corrosion resistance, paired with a high-grade, heat-resistant synthetic float and heat-resistant elastomer seal components for long-lasting reliability