As an alternative to the equations the following graph allows a quick comparison of the effects of changing the area and water velocity. To calculate the permissible height for a site take the actual depth and subtract 0.1 m ( 4") for shallow, high speed flows - those greater than 1.3 m/s ( ~ 4ft/s) and 0.3 m (12") for lower speed flows. There are
2 width (diameter) standards, 1.25m and 2.5m. Other sizes may be accomodated
at a premuim.