The Virginia Graeme Baker Act and also the ANSI/APSP-7 typical deal with entrapment difficulties. The latter states that for residential pools, the water velocity mustn't exceed six ft/sec during the piping inside 3 feet of a suction port and 8 ft/sec in the road likely back again for the pool. https://pool.net/gartenpool-bauen-ohne-betonarbeiten.html