Drain Flow Rate Calculator


About Drain Flow Rate Calculator (Formula)

A Drain Flow Rate Calculator is a tool used to estimate the amount of water that can be drained from a given area over a specific period of time. The Drain Flow Rate formula is used to calculate the flow rate of water that can be drained from a particular area based on the coefficient of runoff, rainfall intensity, and the area of drainage zone.

The formula for calculating Drain Flow Rate is:

DFR = (C * R * A) / 96.23


  • DFR is the Drain Flow Rate in gallons per minute (GPM)
  • C is the coefficient of runoff, which is a measure of how much water can infiltrate the soil and how much flows over the surface. It is a dimensionless value between 0 and 1, where 0 means no runoff and 1 means all rainfall runs off.
  • R is the rainfall intensity in inches per hour (in/hr)
  • A is the area of the drainage zone in acres

The value of 96.23 in the formula is a conversion factor used to convert the units from inches per hour and acres to gallons per minute.

The Drain Flow Rate Calculator takes these inputs and uses the formula to calculate the Drain Flow Rate, which represents the amount of water that can be drained from a specific area in a certain time period. The Drain Flow Rate Calculator can be used by engineers, hydrologists, and other professionals involved in designing drainage systems, stormwater management, and flood control.

The results from the calculator can help these professionals make informed decisions about the capacity of drainage systems and their ability to handle runoff during heavy rain events.


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