Watts 0556031 Valve

The Watts 0556031 (Model LFN36M1-3/4) is a heavy-duty 3/4 inch lead-free vacuum relief valve designed to protect water heaters and supply tanks from atmospheric pressure imbalances. Formerly cataloged under part number 0138458, this updated lead-free version is vital for preventing vacuum conditions that siphon water away, which can lead to heater burnout or catastrophic tank collapse. This valve is engineered with a low profile design and a durable lead-free brass body, making it a reliable choice for tight mechanical spaces in both residential and commercial water service applications.

For high-performance systems, the Watts N36 vacuum relief valve features a silicone disc and a 302 stainless steel spring, ensuring a tight seal under normal operating conditions while opening at less than 1/2 inch of vacuum. It is rated for maximum water pressure of 200 psi and can handle low pressure steam service up to 15 psi at temperatures reaching 250°F. Professionals frequently use this component in jacketed steam kettles, unit heaters, and domestic supply tanks to maintain system integrity and meet ANSI Z21.22 and CSA certification standards.

• Tank Integrity: Prevents internal vacuum build-up to protect against tank siphoning and structural implosion.
• Lead-Free Brass Construction: Complies with potable water regulations, serving as the direct lead-free replacement for the 36A-3/4 and older 0138458 models.
• Versatile Media Handling: Suitable for both water service vacuum relief and low-pressure steam applications up to 15 psi.
• Debris Protection: Includes a protective cap to keep out dust and environmental contaminants from the internal venting mechanism.
• Compact Footprint: The low profile vacuum relief valve geometry allows for installation in confined plumbing headers or cabinet-style water heaters.

Common Questions

Is the Watts 0556031 a direct replacement for the N36-3/4?
Yes, the 0556031 is the lead-free (LF) version of the original Series N36. It maintains the 3/4" MNPT connection and performance specs while meeting modern lead-free requirements for potable water systems.

Where should this vacuum relief valve be installed?
It should be installed in the cold water supply line at a point higher than the top of the water heater or tank it is protecting. Ensure no shut-off valves are placed between the tank and the relief valve.

Can this be used for steam applications?
Yes, it is rated for low-pressure steam systems up to 15 psi. However, when used in steam service, it is recommended to use a pigtail syphon to protect the valve's internal components from direct live steam.

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.