A sump for a swimming pool or spa includes a grate having an elongated slot for inflow of water at a low velocity high flow rate. A housing includes an outlet for conveying water to an oversized suction line to maintain the low velocity high flow rate to the junction with a conventionally sized standard suction line in fluid communication with a suction pump. A bypass line discharges water into the housing when the slot is covered to thereby prevent suction at the slot sufficient to entrap a swimmer against the grate. The grate, a frame supporting the grate on the housing and the housing are devoid of elements that might cause entanglement of hair drawn into the sump. A hydrostatic valve may be coupled with the housing.