Watts 821747 Flanged Dielectric Union 2.5 in Fnpt X Copper

Product Description

The WATTS 821747 is a 2.5-inch lead-free flanged dielectric union designed to isolate dissimilar metals in piping systems and stop galvanic corrosion before it damages the installation. The fitting connects female NPT iron pipe to copper solder-joint (sweat) piping via a cast iron flange tailpiece and an EPDM gasket with standard hardware. It is rated for a maximum working pressure of 50 psi and a maximum temperature of 300 degrees F. Plumbers and pipefitters install this fitting on commercial and residential jobs where code or engineering specs require a dielectric break between ferrous and copper piping.

This union is suited for hot water storage tanks, water heaters, water and air conditioning equipment, processing tanks, and steam, gas, and water distribution piping. It is compatible with water, air, oil, natural gas, propane, gasoline, kerosene, mineral oil, vegetable oil, and alkaline media. The lead-free construction satisfies potable-water compliance requirements in jurisdictions that enforce low-lead plumbing standards.

Key Features

• Dielectric isolation breaks galvanic and stray-current paths between dissimilar metals
• Lead-free cast iron body meets low-lead compliance requirements for potable water systems
• FNPT x copper sweat (C) connection — iron pipe thread on one side, solder joint on the other
• EPDM gasket included with hardware for a complete, field-ready assembly
• Rated to 300 degrees F and 50 psi for broad residential and light commercial coverage
• Compatible with a wide range of media including gas, oil, and water service

Compatibility

Designed as an OEM-style dielectric isolation fitting for 2.5-inch FNPT-to-copper sweat connections in residential and commercial hot water storage, HVAC, and process piping systems where dissimilar-metal joints require galvanic protection.

Installation Notes

Installation should be performed by a licensed plumber in accordance with the International Plumbing Code (IPC) and all applicable local codes. Shut off water supply and relieve system pressure completely before removing any existing fitting or joining the new union. The FNPT end requires thread sealant or PTFE tape; the copper sweat end requires proper flux and solder technique — do not apply torch heat to the assembled union body. Verify that the EPDM gasket is seated evenly before tightening flange hardware.