McDonnell & Miller 250-3/4-30 Valve

The McDonnell & Miller 250-3/4-30 (Part Number 181225) is a high-capacity 3/4" NPT pressure relief valve engineered specifically for hydronic heating systems and storage tanks. Rated for a set pressure of 30 PSI and a substantial 790,000 BTU capacity, this valve provides critical over-pressure protection by utilizing a fail-safe spring-loaded mechanism. Its heavy-duty bronze body and seat, paired with an EPDM rubber diaphragm, ensure resilient performance and chemical compatibility in high-temperature water applications up to 250°F. Designed to meet ASME Section IV boiler and pressure vessel codes, the Series 250 minimizes hammering effects with flash steam while maintaining a low differential pressure of just 3 PSI between opening and closing cycles. For contractors, this means reliable system stabilization and a simplified installation process on any standard ASME pressure relief setup requiring a threaded connection.

• High Thermal Capacity: Handles up to 790,000 BTU, making it suitable for larger residential and light commercial hydronic applications.
• Code Compliance: Fully meets ASME Section IV standards for safety and reliability in boiler systems.
• Durable Construction: Corrosion-resistant bronze body and EPDM internals extend service life in demanding water environments.
• Precision Operation: Low 3 PSI differential prevents excessive short-cycling and protects system piping from shock.

What is the maximum operating temperature for the 181225 valve?
This valve is rated for a maximum fluid temperature of 250°F (121°C), making it ideal for hot water heating systems.

Is this valve compatible with steam systems?
No, the 250-3/4-30 is specifically designed for water media only in hydronic heating systems and tanks.

Can I use this for a potable water system?
This model is typically assigned to non-potable hydronic heating; always verify local lead-free requirements before using it for domestic drinking water applications.

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.