Two farm milk pipelines with weigh jars and milk releasers were rinsed with water sterilized by membrane filtration. Samples of rinse water were collected and analyzed for viable bacteria and coliforms by the membrane filter method. Total aerobic counts averaged 7000/ft2 of milk contact surface in a new milking system during the first month of operation. After 1 year of operation, when certain deficiencies of cleaning occurred, total counts averaged more than 500,000/ft2. Upon correction of deficiencies, average counts dropped to 2000/ft2. Counts of coliforms in clean systems averaged less than 1/ft2. Gram negative bacteria constituted only 5% of the microflora in rinses from a system that had been in operation for 4 years; whereas, 67% of the colonies were micrococci and 22% were streptococci. Use of the filtration system for preparation of sterile water is discussed.

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