McDonnell & Miller 318826 O-Ring

The McDonnell & Miller 318826 O-Ring (Model 69-113) is a critical sealing component engineered specifically for Series 69 and E8 liquid level controls. Designed for the rigorous environment of low-pressure steam boilers, this industrial-grade elastomer gasket ensures a high-integrity, leak-free seal between the boiler nipple insertion tube and the float assembly housing. This "New Style" square-cut gasket replaces older round profiles to provide superior compression and retention under pressure, maintaining the vacuum and pressure thresholds required for accurate Low Water Cut-Off (LWCO) functionality.

For service contractors performing annual inspections, the 318826 is the standard replacement to prevent external steam leaks and potential nuisance shutdowns. This OEM McDonnell & Miller replacement part is built to withstand chemical treatment in hydronic systems and the thermal cycling common in commercial heating applications. Proper installation is essential for the Series 69 mechanical LWCO to monitor water levels safely, protecting the heat exchanger from dry-fire conditions. Ensure the seating surfaces are clear of scale before positioning the o-ring to guarantee a performance-grade seal.

• Precision Fit: Specifically machined for McDonnell & Miller 69 Series and E8 float-type controls.
• Square-Cut Design: Enhanced "New Style" profile offers greater surface contact than traditional round o-rings for an airtight seal.
• Steam-Rated Durability: Constructed from high-temp elastomers to handle boiler nipple heat and pressure.
• System Security: Prevents bypass leaks that could interfere with the critical low water cut-off safety sequence.

• Is this compatible with the Series 67? No, this o-ring is specifically designed for the 69-113 assembly; the Series 67 typically utilizes the 67-12 gasket.
• Does this include the square-cut update? Yes, the 318826 is the updated square-cut gasket, providing a more robust seal than legacy round versions.
• When should this o-ring be replaced? It should be inspected annually and replaced whenever the float assembly is pulled for maintenance or if any moisture is detected around the insertion tube.

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.