Which component must accompany a double check assembly when installed below grade?

Which component must accompany a double check assembly when installed below grade?

• A. Check valve
• B. Air vent
• C. Isolation valve
• D. Wye strainer

Answer: (D)

When a double-check backflow assembly is installed below grade, debris and sediment in the line can easily reach the device. A Wye (Y) strainer placed upstream acts as a filter, capturing particles before they enter the backflow preventer. This protects the internal valves and seals from clogging or damage and helps ensure reliable operation, especially in underground installations where dirt and roots are more likely to be present. The strainer is also usually serviceable from above ground, making maintenance easier. The other components aren’t required as a companion for this setup: the double-check itself contains the necessary valves, an air vent isn’t typically needed for underground installations, and while an isolation valve can be used for servicing the unit, it isn’t mandated as the accompanying component of the assembly.

When a double-check backflow assembly is installed below grade, debris and sediment in the line can easily reach the device. A Wye (Y) strainer placed upstream acts as a filter, capturing particles before they enter the backflow preventer. This protects the internal valves and seals from clogging or damage and helps ensure reliable operation, especially in underground installations where dirt and roots are more likely to be present. The strainer is also usually serviceable from above ground, making maintenance easier.

The other components aren’t required as a companion for this setup: the double-check itself contains the necessary valves, an air vent isn’t typically needed for underground installations, and while an isolation valve can be used for servicing the unit, it isn’t mandated as the accompanying component of the assembly.