Magnesium Anode Rod 3/4" x 42" with Hex Plug | Replaces Rheem AP12938 | NBK-21027

NBK-21027 – Magnesium Anode Rod 3/4" x 42" with Hex Plug | Replaces Rheem AP12938

The NBK-21027 Magnesium Anode Rod is an essential corrosion-protection component for outdoor wood boilers and water heater tanks. By attracting corrosive minerals and electrochemical activity away from the tank walls, the sacrificial magnesium rod quietly does its job — extending tank life, preventing rust, and protecting your investment season after season. At 42 inches long with a standard 3/4" hex plug, it’s a direct drop-in replacement for Rheem AP12938 and Grainger 45W630.

Key Features

• Magnesium Construction – Superior sacrificial anode material that actively attracts corrosive elements to protect tank walls
• 3/4" Hex Plug – Standard connection size compatible with most outdoor boiler and water heater tanks
• 42" Length – Full-length coverage for maximum tank protection and extended service intervals
• Direct OEM Replacement – Drop-in replacement for Rheem AP12938 and Grainger 45W630
• Extends Tank Life – Regular anode replacement is the single most effective way to prevent premature tank failure

Specifications

• SKU: NBK-21027
• Part Number: SO-21027-NBK
• Material: Magnesium
• Plug Type: 3/4" Hex Plug
• Rod Diameter: 3/4"
• Rod Length: 42"
• Application: Outdoor wood boilers, water heater tanks

Replaces / Cross-Reference

• Rheem: AP12938
• Grainger: 45W630

Common Applications

• Outdoor wood boilers and biomass boilers
• Residential and commercial water heater tanks
• Any hot water system requiring sacrificial anode corrosion protection

Installation Tips

• Turn off the water heater or boiler and allow the system to cool before servicing
• Relieve tank pressure before removing the existing anode rod
• Apply thread sealant or plumber’s tape for a leak-free installation
• Inspect anode condition annually — replace when more than 50% depleted for best protection

Why Choose the NBK-21027?

A depleted anode rod is the leading cause of premature water heater and boiler tank failure. The NBK-21027 restores full corrosion protection with a full-length 42" magnesium rod — the same specification as Rheem AP12938 — at a fraction of the OEM cost. A simple annual inspection and timely replacement can add years of life to your tank.

SPECIAL ORDER NOTICE: This item is sourced through our special order program. Please allow 1–2 business days for processing prior to shipment.