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How to size the sump pump for waste water collection such as storm drain & subsoil drain?

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How to calculate size of water collection sump in basement either for sewage collection or storm water collection
asked Feb 26, 2015 by anonymous

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Sewage pump is for sanitary waste and sump pump is for storm drain (rain water) and wastewater such as underground water collection for protecting the building foundation. The sewage pump sizing is already one of the answered question. Below is sump pump sizing:


Sump pump sizing


  1. Calculate the amount (gpm) of storm drain per local rain fall record (the storm drain load calculation should be under separate question).  
  2. Estimate the underground water collection (civil can estimate per local rain fall record) and other non-sanitary wastewater load (gpm).


  1. The Static Head: The actual vertical distance of “lift” in feet from the minimum water level in the basin to the highest point in the discharge piping.
  2. The Friction Head: The friction losses caused by pumping the fluids through the various piping and fittings. 

Selecting the Pump:

Using the Capacity (GPM), Total Dynamic Head, and solids handling requirements, refer to the pump performance curves to determine the best pump for the application. Select the smallest pump that meets the Capacity and Head requirements. 

Basin size

To determine the proper basin size, refer to the required GPM of the system, convert this to the volume the pump must be able to pump out of the basin during each cycle using formula:  

                     GPM x Run Time (min.) = Volume (gals)

The run time must be at least 2 minutes to ensure against short cycling (which would greatly reduce the service life of the pump).  

Pump Quantity:

Most commercial applications requires duplex pump systems to guaranty stand –by safety factor that many municipalities require (public health concern). In most residential installations, a simplex system is adequate. Exact requirement shall be verified with the local plumbing and municipal codes. 

answered Mar 1, 2015 by Matt Hall

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