Non-priming pumps are best used in flooded suction applications. This means the pump sits below the water level it is pumping. Examples would be alongside of a fish tank or in a pump chamber buried alongside of a pond. These pumps can sit above the water level, however, a check valve must be used on the end of the suction line to keep the pump primed.
Self-priming pumps have the capability of purging some air from the suction line and priming themselves (after filling the pump with water the first time). These pumps can sit above the water level without a check valve in the suction line, however, using a check valve speeds up the priming process and ensures a quick flow when the pump is plugged in. Following is a comparison chart between our most popular external pumps. Use this chart to help select which pump is best for your application. Start by finding the feet of head column on the right side of the chart. Look down the numbers under the feet of head in your application to find a pump that provides the amount of water needed.
Tips for operating an External Pump:
Proper plumbing selection and set up is important when choosing to use an external pump. There are two basic set ups with an external pump: flooded suction or suction lift. A flooded suction set up is where the pump is situated below the water level and the water flows by gravity to the pump. A suction lift set up is where the pump is located above the water level. “Suction lift” is a technical term for this set up, it does not mean that the pump acts like a vacuum cleaner. To the right are some ways to set up an external pump with a skimmer. There are limits to how high a pump can be placed in a suction lift set up. Each pump is different, but these general layouts show how an external pump can be used.
