Backflow Preventer Sizing: 1" Valve on 3/4" Supply? Use 1" Throughout

Pipe Sizing Myth: Reducing Size Doesn't Increase Pressure

3/4" meter, 3/4" supply, 60 PSI. Have 1" Watts 800M4FR backflow. Can you use 1" valves and pipe?

Yes—Run 1" Main & Laterals

• Reducing pipe size saves money only, doesn't boost pressure.
• 1" pipe at 8–10 GPM has negligible friction loss.
• Simplifies fittings inventory (one pipe size, one fitting size).

Connection at Backflow

Use 3/4" x 1" female adapters on backflow inlet/outlet. Add unions for serviceability.

Valve Recommendation

Avoid jar-top valves (leaky, poor performance). Use:

• Orbit 1" FNPT inline/angle with flow control (Home Depot).
• Rain Bird DVF 1" (supply house).
• Best: Rain Bird PGA 1" angle pattern (pro grade).

Velocity Check

Ensure no pipe runs < 20 ft (velocity noise/hammer risk).