Check the listing for details. Watts 1/2" Threaded Dual Check Backflow Preventer w/ Atmospheric Vent. Condition: New – Open box. Listed at 75.00 USD. The Watts 1/2" Threaded Dual Check Backflow Preventer with Atmospheric Vent is a reliable and efficient solution for preventing backflow in plumbing systems. With its double check assembly design, this unit offers a higher level of protection against potential contamination. The atmospheric vent feature ensures proper ventilation, making it a practical choice for various industrial and commercial applications. Watts is a trusted brand known for producing high-quality piping products, making this backflow preventer a dependable option for maintaining clean and safe water systems.