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Bronze dual check valve with FNPT union connections

Watts

Watts 9D-M3-1/2 Dual Check Valve Trap

SKU CH-YEMT-ZJNJ0 MPN 9D-M3-1/2

Dual check valve with atmospheric vent, brass body, FNPT union connection, rated to 250 degrees and ASSE 1012 standard

  • TypeDrain Components
  • Dual-check design stops backflow for safer water supply
  • Atmospheric vent prevents vacuum formation during pressure drops
  • Brass body withstands 250°F for reliable hot-water service
  • FNPT union connection simplifies installation and maintenance
  • Certified to ASSE 1012 and CSA B64 standards

Dual Check Valve with Atmospheric Vent

The Watts 9D-M3-1/2 is a bronze backflow preventer designed for plumbing systems requiring protection against low-hazard contamination. Its FNPT union connections allow straightforward installation in residential or light-commercial water lines. The unit meets ASSE 1012 and cCSAus standards for dual-check-valve assemblies. Builders needing a compact, code-compliant device for cross-connection control will find it suitable.

Operating Temperature and Pressure Limits

The brass body is rated for a maximum working temperature of 250 degrees Fahrenheit, covering typical hot-water distribution temperatures. Standard supply pressures keep the check mechanisms seated without chatter or excessive pressure drop. The atmospheric vent provides a visual indication of check-valve failure without discharging water under normal conditions. No electrical power or external control is required for operation.

Sustained High-Temperature Performance

Under continuous hot-water circulation up to the 250-degree rating, the internal elastomers maintain sealing integrity without accelerated degradation. The dual-check design ensures that if one check fouls with debris, the second continues to prevent backflow. The atmospheric vent remains clear to signal any sustained leakage past either seat. Systems experiencing frequent thermal cycling stay protected without periodic reset or manual intervention.

Highlights

  • Dual-check design stops backflow for safer water supply
  • Atmospheric vent prevents vacuum formation during pressure drops
  • Brass body withstands 250°F for reliable hot-water service
  • FNPT union connection simplifies installation and maintenance
  • Certified to ASSE 1012 and CSA B64 standards

Specifications

TypeDrain Components
BrandWatts
Model9D-M3-1/2"

Questions about this item

How is the 1/2 in FNPT union connection installed, and what step is often missed?

Thread the union onto the pipe using pipe thread sealant, then tighten to the manufacturer's torque specification; the step often missed is checking that the atmospheric vent port faces upward after final alignment.

What maintenance will the dual check valve and atmospheric vent need later?

Inspect the check discs and vent screen annually for debris or mineral buildup; clean or replace the internal components if flow becomes restricted or backflow prevention fails.

What limit appears first when the valve runs continuously at high temperature?

The 250 °F maximum temperature rating is the primary limit; sustained operation above this can degrade the brass body and check valve seals, leading to leakage or loss of backflow protection.

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