This standard covers two types of backflow prevention devices capable of withstanding a water working pressure of 150 psi without damage to working parts or impairment of function and for operation on hot- or cold-water lines. This standard covers devices designed to operate with water at a temperature range of 33ºF to 110ºF (1- 43ºC). The manufacturer should be consulted if higher temperatures are encountered. A complete device includes the reduced pressure principle and the double check valve type. Major revisions to this edition include: the definition of a reduced pressure principle type device, in Sec. 1.1 Scope, was reworded to clarify meaning; requirements for a certificate of approval have been added that cover laboratory and field evaluations and renewals of the certificate; allowable pressure losses for the reduced pressure devices have been reduced 35-44 percent; the rated flow for the 1/2-in. reduced pressure device has been reduced from 20 to 12 gpm, and the minimum discharge from the relief valve has been reduced from 5 to 3 gpm; removal from the line for servicing of 2 in. and smaller devices has been permitted; the number of materials covered by detailed specifications has been reduced to nine, and the use of other materials is permitted, subject to approval by the approving agency; and, manufacturers are required to attach a tag to each unit giving clear installation instructions (Sec. 4.2.8).