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3-1/2" Union Nut Black 98212200Z

Ensure a rock-solid, leak-free connection for your pool equipment with this professional-grade 3-1/2 inch union nut. Specifically engineered for large-format filtration systems, this replacement nut provides the clamping force needed to secure 2-inch and 2.5-inch plumbing unions to the filter tank. Molded from high-impact, glass-reinforced thermoplastic, it is built to withstand extreme pressure surges and harsh chemical environments without stripping or cracking. The architectural black finish is UV-stabilized to prevent brittleness from sun exposure, making it an essential component for maintaining a safe and efficient equipment pad.

Specifications

Replacement 3.5-Inch Filter Union Nut

Professional-grade original spec replacement union nut specifically engineered for large-format pool filtration systems. Molded from glass-reinforced, UV-stabilized thermoplastic, it provides the essential clamping force needed for leak-free high-flow plumbing connections.

Internal Thread 3.5" (Standard Buttress)

Material Glass-Reinforced Polymer

Color Architectural Black

Pressure Rating Engineered to 50 PSI

Cartridge Fit Clean & Clear Plus, RP

D.E. Fit FNS Plus, Quad D.E.

Grip Design Vertical Ribbed Torque

UV Protection UV-Stabilized Compound

Safety Warnings & Critical Care

Pressure Release: NEVER loosen this nut while the pump is running or the tank is under pressure. Always open the air relief valve until the gauge reads zero before servicing.

No Pipe Wrenches: This nut is designed for hand-tightening. Using large wrenches or channel locks can crack the housing or "ovalize" the nut, leading to permanent leaks.

Heat Sensitivity: If the pump has run dry and created hot water, allow the system to cool completely before turning. Heat expansion makes removal nearly impossible without damage.

💡 Pro-Tips for Successful Installation

The "Two-Hand" Turn: Always start the threads by hand to ensure perfect alignment. Cross-threading large plastic threads can permanently ruin the expensive bulkhead.
Lubrication is Essential: Apply silicone-based lubricant to the threads and the face of the nut where it contacts the tailpiece to reduce friction and improve the seal.
Winter Storage: If disconnecting plumbing for the winter, leave the nut loosely threaded onto the bulkhead to protect threads from damage or debris.
Verification: This large-format nut is typically used on high-capacity tanks; smaller 50/75 sq. ft. filters often use a different thread size.