How to Determine Water Flow in a Fountain Spillway

Rectangular Spillway

• 1

  Measure the width of the spillway and the height of the flow across the top of the spillway in inches. Measure the flow height in the middle and at both ends to see if there are differences. Use an average height if measurements vary by 1/8 inch or more.

• 2

  Multiply the width times the height. Multiply this number times 3.33 to get the flow in gallons per minute, or gpm. If you need to change the number gallons per hour, multiply gpm times 60.

• 3

  Determine the pump location and the height to which the water which must be pumped. Locate a pump that has the required flow rate and look at its pump curve at the required feet of head. If this pump doesn't fit your flow requirements, look at other models suitable for your application.

Circular Spillway

• 4

  Determine the circumference of the spillway in inches. This can be done with a tape measure by two or more people by following the circumference of the fountain. Alternatively, you can calculate it using the formula, C = 2 x π x r, where C is the circumference, π is 3.14, and r is the radius (1/2 the diameter).

• 5

  Measure the water height at top of the spillway. Measure the height in different locations if the surface is irregular and average these measurements.

• 6

  If a circular spillway has irregularities and water only flows through low points, physical measurement is required. Determine the length of the spillway portion being sampled, find the volume collected per minute and adjust the gpm for the total spillway length. Multiple samples can be averaged for a more accurate flow estimation.

• 7

  Calculate the flow in gallons per minute by the formula: gpm = width x height x 3.33. Multiply this result by 60 to convert gpm to gallons per hour, or gph.