SumpPumpsUSA - Guidelines for Sizing a Sump Pump

Question
Do you have any guidelines for properly sizing a pump?

Answer
The longer the pump runs and the longer it is off, the better.  For replacement pumps: If the pump you are replacing had a run cycle that sufficiently removed water from your sump pit, without high volumes of on off cycles, then it's safe to assume that you can replace your existing pump with a pump of the same HP rating.  If your existing pump has difficulty keeping up with the water volume and cycles on and off frequently, a pump with a larger HP rating may be required..

For drain tile, there is a calculation that uses the square foot of the area that feeds the drain tile and a 100 year flood rule, based on geographic location.  Being that it would be impossible for to know all the details of the installation and local codes, sizing is typically left up to the installing contractor. Installing contractors typically make a site visit to properly calculate the size requirements of the site…

Question

Do you recommend over-sizing a sump pump?

Answer

No. Generally, the longer the pump runs and the longer it is off, the better.

If your pump is over-sized, the pump will have a shorter run-cycle.  The pump will turn on, empty the pit and turn off in a shorter period of time   With heavy flow coming into the pit, the sump pump will not stay off for very long.  The constant on/off of the pump dramatically shortens the life of the pump.

When a pump properly sized, the pump will cycle on and empty the pit for a longer duration of time.  With heavy flow coming into the pit, the pump will have time in between cycles to cool down and produce less cycles over the lifetime of the pump