When using a plunger or piston pump, there is always a chance of leakage. The advantage of using a diaphragm pump is the elimination of leakage. The reciprocating motion is created the conventional way. The motion from the crosshead is transmitted directly to a diaphragm.

In the picture, the liquid would come through the lower ball valve and flow towards the upper ball valve exiting the pump. Mechanical diaphragm pumps are also constructed vertical. Most of these pump only have a single cylinder, but twin cylinder pumps are available. The single cylinder vertical type pump can also be referred to as single disc pumps.

The vertical pump can be constructed with a spring-loaded coupling incorporated in the connection rod. The spring loading allows the diaphragm to short stroke if large solids restrict the diaphragm motion. This pump is popular as a site pump, since it can be engine driven. The pump is applicable when using a low pressure pump. The pump can handle up to 6 bar. The low pressure reciprocating pump has some distinct advantages over the piston and plunger pumps. They are self-priming and have suction lift capabilities up to 6 meter. The pump can run dry without causing any damage to the pump. The valves are based on the liquid the pump has to process, whether the liquid is high-viscous or contain large solids.

There is a special pump derived from the mechanical diaphragm pump that has been developed to handle viscous liquids and solid handling. These pumps have two rubber diaphragms which are used as a pumping element and valves.
The first diaphragm opens and allows the liquid flow into the pumpchamber. When the diaphragm closes, the liquid is trapped in the pumpchamber. At the same time, the second diaphragm opens. The liquid flow into the discharge system when the second diaphragm closes.