It is very important to know what makes the difference between one diaphragm pump and another. Ideally, you should make sure that you buy from a reputable diaphragm pump manufacturer & supplier. Once you find a good company, it is time to go through their products. The pump motor requires special attention. A pump can be driven by all kinds of rotational motors. It makes no difference if they are electric, hydraulic, air or based on internal combustion. Some units are actually driven by the other side of the diaphragm, hence the importance of air pressure. Go through each category before deciding.