http://www.gmbpumps.com/ water pump, water pumps,submersible water pump,sta rite well pumps,constant pressure well pump A water pump is a device used to raise, compress, transfer and move water and other fluids, such as liquids and slurries. These devices are available in a variety of designs and horsepower. These pumps can be classified in three major categories, including displacement, direct lift and gravity pumps. All these machines basically serve the same purpose of moving water from one point to another.