<human>:  What is the difference between a diaphragm pump and a piston pump?
<bot>: A diaphragm pump is a positive displacement pump. A piston pump is a positive action pump. A diaphragm pump uses a flexible diaphragm to create a seal between the pump and the fluid being pumped. This allows the pump to create a vacuum, which draws the fluid into the pump. A piston pump uses a piston to create a seal between the pump and the fluid being pumped. This allows the pump to create a positive pressure, which pushes the fluid out of the pump.