The water flow calculator is a one sided, cardboard sheet, featuring a circular slide and a secondary slide, mounted using a metal screw. The chart is used for indicating the diameter and length of pipes necessary to regulate water flow. The backing board features, partially handwrtten, an arched scale for indicating the velocity in feet per second and the amount of water discharged in cubic feet of a pipe. The arch is curved to fit the circular slide attachment, which can be rotated 360 degrees and contains two scales, for diameter of pipe and length of pipe. The centre of this slide contains a set of instructions on the usage of the chart. Below the circular slide, the additional slide attachment can be rotated and features a head of water scale for measuring the maximum height the pump can raise the water to. At the bottom of the chart is the final scale, used to line up the diameter of the pipe.
"K. SMIT" handwritten in top right corner.
"G.M. Ritchie / 21/6/21" handwritten in centre, under circular slide.