Swimming Pool Main Drains & Flow Rate

In private pools, Each individual Drains are anywhere where between 8 - 15 m3 /H with 50mm and 63 mm pipe diameter. Where as i commercial pools the rates are 12 -15 m3/h with 63 mm and 75 mm Piping diameter. flow rates in commercial pools are calculated assuming a flow rate of 0.3m3/h/m2 at the drain grate and a maximum flow rate of 1.5 m/sec in the pipe carrying the water to the filters.