The SCWD (pronounced "squid") is a revolutionary device designed to provide alternating currents without the use of electricty. The SCWD mounts inline with 3/4" tubing, the two ports alternate the output, the bottom port is the input. A great alternative to expensive electronic ball valves. The SCWD will run on any pump with a minimum output of 50 GPH and a maximum output of 1400. The switching speed and current duration is dependent on the volume of water flowing through the SCWD. You can control the duration by controlling the flow going through the SCWD. Can be submersed for use with large power heads or used externally.SCWD is regarded by industry experts as the most energy efficient wave-making product on the market. It replicates nature by generating alternating currents within a tank or pond. These currents stimulate coral, fish, and plant growth and keep other aquatic life healthy because of the tank or pond? increased water currents and oxygenation.A great product with a full 90-day manufacturer`s warranty. Flow into SCWD SCWD TD Output Efficiency Switching Duration 150 gph 90 gph 60% 22 seconds 180 gph 120 gph 65% 16 seconds 240 gph 180 gph 75% 12 seconds 270 gph 210 gph 80% 10 seconds 330 gph 240 gph 80% 9 seconds 400 gph 360 gph 90% 7 seconds 600 gph 540 gph 90% 5 seconds 720 gph 660 gph 90% 4 seconds