WATERWORKS INTERNATIONAL

NOTES:

• Most states now recommend water velocities of 1 1/2 - 2 ft. per second at the grate to prevent entrapment.
• Anti-Vortex covers reduce open area.
  Example: A 12" x 12" standard frame and grate has an open area of 85 Sq. In.
  A 12" x 12" frame and anti-vortex plate has an open area of 31.5 Sq. In.
• To maintain 1 1/2 - 2 Ft./Sec. velocities, use a flow rate of 4 1/2 GPM for each Sq. In. of grate area.
  
  

  	Examples	Open Area	Max. Flow Rates
  8"	Round Main Drain w/ Anti-Vortex Cover	7 Sq. In.	30-35 GPM
  9" x 9"	Square Main Drain w/ open Frame & Grate	49 Sq. In.	220-230 GPM
  12" x 12"	Square Main Drain w/ open Frame & Grate	85 Sq. In.	400-410 GPM
  12" x 12"	Square Main Drain w/ Anti-Vortex Plate	31 Sq. In.	135-145 GPM
  18" x 18"	Square Main Drain w/ open Frame & Grate	196 Sq. In.	900-920 GPM

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