McDonnell & Miller 310800 Gasket

The McDonnell & Miller 310800 Gasket is a critical sealing component engineered specifically for the 21 Series and 221 Series float-operated water feeders. Also identified by model number 21-12, this 4-hole valve body gasket provides a high-integrity seal between the valve assembly housing, the strainer body, and the feeder flange. In steam and hot water boiler applications, maintaining a leak-proof connection at the make-up water feeder is essential to prevent pressure loss and ensure the float mechanism responds accurately to changing water levels.

Constructed from durable, high-grade materials resistant to the thermal stresses of hydronic systems, this replacement gasket is designed for a precision fit to eliminate bypass leakage. During routine maintenance or when replacing the SA21-6 valve assembly, technical standards dictate the use of a new 310800 gasket to ensure proper compression. Following manufacturer specifications, mounting bolts should be tightened to 16 ft/lbs to maintain the seal under maximum vessel pressures of up to 35 PSIG and water supply pressures reaching 150 PSIG. This genuine McDonnell & Miller 21-12 part ensures your feeder maintains its proportional feed action without environmental interference.

• Precision Compatibility: Specifically engineered for a perfect fit on McDonnell & Miller Series 21 and 221 water feeders.
• Leak Prevention: High-density material provides a reliable valve body seal, preventing external leaks and internal pressure bypass.
• Thermal Resistance: Rated to withstand the standard operating temperatures of residential and commercial boiler receiver tanks.
• OEM Standards: Guarantees the structural integrity of the feeder housing when torqued to 16 ft/lbs.

When should the 21-12 gasket be replaced?
Technicians should replace this gasket every time the valve assembly or strainer body is removed for inspection, or if any moisture is detected at the housing seams during annual maintenance.

Is the 310800 gasket compatible with the 221 model?
Yes, the McDonnell & Miller 310800 is the correct valve body gasket for both the 21 and the 221 float-operated water feeders.

What is the correct torque for the mounting bolts?
To achieve a secure, uniform seal without damaging the gasket or housing, all mounting bolts should be hand-secured and then cross-tightened to a final torque of 16 ft/lbs.

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.