Pull a Vacuum : (1) A term that refers to the partial vacuum that exists when a pump is exceeding the capacity or yield of a hydrant. (2) To reduce the pressure between the pump and the water supply. See also: Cavitation and Drafting
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}