| (153) Vacuum--The reduction of atmospheric pressure within a pipe, tank, pump, or other vessel. Vacuum is measured in inches of mercury. Each inch of mercury is equivalent to 1.13 feet of head. The typical maximum vacuum is 30 inches of mercury, or 33.9 feet of head. (154) Valve--Any device in a pipe that will partially or totally obstruct the flow of water (as in a ball, gate or globe valve) or permit flow in one direction only (as in a check or foot valve). See definitions (23) "Bleeder valve", (78) "Multi-port valve", and (110) "Push-pull valve". (155) Velocity--The speed at which a liquid flows between two specified points, expressed in feet per second. (156) Vortex pool--Circular pools equipped with a method of transporting water in the pool for the purpose of propelling riders at speed dictated by velocity of the moving stream. (157) Wading pool--A Class D pool that has a maximum depth of 2 feet at any point. (158) Walls--The interior pool or spa wall surfaces consisting of surfaces from plumb to a slope of 11 degrees from plumb. (159) Waste water disposal system--A plumbing system used to dispose of backwash or other water from a pool or spa or from dressing rooms and other facilities associated with a pool or spa. (160) Water action pools--A pool designed to simulate breaking or cyclic waves for the purpose of general play or surfing. (161) Water lounge--A horizontal area of a pool that adjoins the pool wall at a depth of from 2 inches to 10 inches, is used for seating and play. (162) Weir--Part of a skimmer that adjusts automatically to small changes in water level to assure a continuous flow of water to the skimmer. (163) YMCA--Y.M.C.A. of U.S.A. (Y.M.C.A.), 101 North Wacker, Chicago, Illinois 60606, telephone (800) 872-9622. (164) Zero depth entry pool--A pool in which the pool floor intersects the water surface along at least one side of the pool. |
