M-a-57: Use of Auxiliary High Pressure Water Pumps on Grade "A" Dairy Farms
200 C Street, SW
Washington, DC 20204
October 24, 1975
Revised August 17, 1979
TO: All Regional Food and Drug Directors
Attn: Regional Milk Specialists
FROM: Chief, Dairy and Lipid Products Branch (HFF-415)
SUBJECT: Use of Auxiliary High Pressure Water Pumps on Grade "A" Dairy Farms
We have had recent requests regarding the use of auxiliary water pumps to increase water pressure in milk houses, dairy barns and milking parlors. These pumps increase the water pressure and permit easier cleaning of floors, walls stantions, stalls and the exterior surfaces of equipment. However, they can create a negative pressure in the water supply system because of their capability to pump at a faster rate than water can be supplied if not properly installed and operated.
When a negative pressure exists in the water supply system there is a possibility for contamination to enter the water system due to backsiphonage. This is considered a violation of Item 8r of the 1965 Grade "A" Pasteurized Milk Ordinance, 1978 Edition
An auxiliary high pressure water pump may be used if it is protected in one of the following ways:
- The auxiliary pump may be supplied by a separate surge tank that is isolated from the main water supply system by an air gap.
- The auxiliary pump may be supplied by a separate water source that is not connected to the water supply system supplying water to the milk house.
- An effective low pressure cut-off switch may be installed on the suction side and immediately upstream from the pump. This switch must deactivate the pump when the pressure on the suction or feed line drops below 10 pounds per square inch.
- The installation of any other device or means that will satisfactorily prevent a negative pressure on the water supply system and subsequent contamination of the water supply system.
Copies of this memorandum are enclosed for distribution to the State milk control agencies and to State Milk Officers in your Region.
Eugene T. McGarrahan