When looking for a vacuum pump there are several questions that you should be considering. First you need to establish weather or not you need a diaphragm pump or an actual vacuum pump. This question can be addressed by knowing the following:
Vacuum Pumps: What You Should Know

Diaphragm Pump Technology Advances

Diaphragm pump technology for wastewater pumping, waste oil, septic and food processing applications has advanced. Wastecorp, a designer and manufacturer of diaphragm pumps, has invested in R&D to build better diaphragm pumps.
