Diaphragm pumps are called positive displacement pumps because they pump a specific volume for each pump cycle. Diaphragm pumps move fluids more slowly than centrifugal pumps, but they can handle thicker mud and larger amounts of solids including abrasive materials. They can tolerate air being drawn into the pump, and can be run dry without damage. Widely used to control slow seeping in evacuations, pumping out septic systems. The rubber elastomer diaphragm and flapper valves are easily replaced on site.