Changes

A major advantage of these pumps is variable pumping at constant speed, because the output (up to design capacity) is controlled by the sump level and equals the influent flow rate. The disadvantages are the inducement of turbulence, the release of odors and other volatile substances (if using for wastewater), and the relatively high initial cost (if using metal components, but not wooden). But when comparing costs with those of other types of pumps, consider the cost of the total system, including all piping, wet or dry wells, screens, fittings, valves, variable-speed controls, and other accessories as well as operating and maintenance costs. Note that operators like screw pumps because the good ones, when properly installed, are so trouble-free.<ref> [http://uotechnology.edu.iq/dep-building/LECTURE/sanitary%20&%20environmental/third_class/Water%20Networks%20and%20Equipment/D-pumps-3rd%20Class.pdf Pumps and Pumping Stations, 3rd Class. ] By Dr. Sataa Al-Bayati. University of Technology - Iraq.<ref/>