Vacuum filtration is a laboratory procedure involving the collection of particulate from a suspension usually a bacteria or precipitate. The suspension passes through filter paper of a known pore size which retains the bacteria or particles. The filtration equipment used for this procedure consists of an oil-free vacuum pump, filter apparatus, filter flask and often a filtration manifold. The membrane filtration technique utilizes vacuum filtration and is an accepted technique for testing fluid samples for contamination. The membrane filtration technique was accepted by the U.S. EPA for microbial testing and is the preferred technique for water testing.