Let the Quick Valve do the filling and draining and you can leave the tray to get on with it. It is a patented automatic valve. The clever part: as the tray fills, the valve drags extra oxygen into the nutrient water on its way past. Roots love that, and you see it in stronger leafy greens and herbs.
On the drain stroke a siphon kicks in and shifts about 28 litres a minute, so the bed empties fast and right to the bottom. The inlet is 4mm, the outlet 3/4 inch, on a 1/2 inch, 18mm connection. At 1 bar pump pressure you get 9.2 litres a minute. PP and PVC body, 12.5mm hose.