It all depends on how much water you need to pump, how quickly you need to pump it, and how dirty the water is. A pump’s performance is determined by many factors such as atmospheric pressure (how high the pump is above sea level) resistance from hoses, etc. A pump’s performance is measured in flow and expressed in gallons per minute or gallons per hour. The higher the flow, the better the performance. If the water is sandy, muddy (abrasive), or has small particulates, you should purchase a semi-trash or trash pump. If the water you intend to pump is always clean, such as in a swimming pool, hot tub, or water garden, a clean water pump will be fine.