| (A) Steps--A riser/tread or series of risers/treads extending down from the deck and terminating at the pool or spa floor. Included are recessed steps that have the risers located outside of user areas. (B) Ladders--A series of vertically separated treads or rungs connected by vertical rail members or independently fastened to an adjacent vertical pool or spa wall. (See definition (73) "Ladders" for particular ladder types.) (C) Recessed treads--A series of vertically spaced cavities in the pool or spa wall creating tread areas for step holes. (131) Suction outlet--The aperture or fitting through which the water is drawn from the pool or spa. A skimmer is not considered a suction outlet for purposes of these rules. (132) Super chlorination--The practice of adding a sufficient amount of chlorinating compound to water to destroy chlorine demand compounds and any combined chlorine that is present. Generally, the level of chlorine added is 10 times the level of combined chlorine in the water. (See also definition (26) "Breakpoint chlorination".) (133) Surface skimmer system/Through wall skimmer--A device installed in the wall of an in-ground pool or spa, or above-ground pool or spa that permits the continuous removal of floating debris and surface water to the filters. (134) Surge pit--A collecting tank or sump that allows the pool drain(s) and surface collection system to flow into it by gravity. (135) SVRD--A safety vacuum release device, as described in §296.190(d)(3)(B) of this title for minimizing risk of entrapment. (136) SVRS--A safety vacuum release system that consists of either an SVRD or an AVS, as described in §296.190(d)(3) of this title for minimizing risk of entrapment. (137) Swimout--A recessed area outside of the general perimeter of the pool designed to facilitate the entry and exit of swimmers from a pool. (138) TCEQ--Texas Commission on Environmental Quality, P.O. Box 13087, Austin, Texas 78711-3087, telephone (512) 239-1000. (139) TDLR--Texas Department of Licensing and Regulation, Boiler Division, P.O. Box 12157, Austin, Texas 78711, telephone (800) 803-9202. (140) TDS--Total dissolved solids, i.e., a measure of the total amount of dissolved matter in water (for example, calcium, magnesium, carbonates, bicarbonates, metallic compounds). (141) Test kit--A device for monitoring a specific chemical level in pool or spa water. (142) Therapeutic pool or spa--A pool or spa that is operated exclusively for therapeutic purposes, such as physical therapy, and is under the direct supervision and control of licensed medical personnel. (143) Total alkalinity--A measure of the ability or capacity of water to resist change in pH; also known as the buffering capacity of water. Measured with a test kit and expressed as ppm; consists mainly of carbonates, bicarbonates and hydroxides. (144) Total chlorine--The sum of both the free available and combined chlorine. (145) Toxic--A substance that has an adverse physiological effect on human beings or other living organisms. (146) Turbidity--Cloudy condition of water due to the presence of fine particulate materials in suspension that interferes with the passage of light. (147) Turnover rate--The period of time (usually in hours) required to circulate a volume of water equal to the total pool or spa capacity. (148) UFC--Uniform Fire Code, published by the International Fire Code Institute, 5360 Workman Mill Road, Whittier, California 90601-2298, telephone (800) 423-6587. (149) Underwater light--A fixture designed to illuminate a pool or spa from beneath the water surface. An underwater light includes either of the following: (A) wet niche light--a watertight and water-cooled light unit placed in a submerged, wet niche in the pool or spa wall and accessible only from the pool or spa; or (B) dry niche light--a light unit placed behind a watertight window in the pool or spa wall. (150) UL--Underwriters Laboratory, 333 Pfingsten Road, Northbrook, Illinois 60062-2096, telephone (847) 272-8800. (151) User--A person using a pool or spa and adjoining deck area for the purpose of water sports, recreation therapy or related activities. (152) User load--The number of persons in the pool or spa area at any given moment, or during any stated period of time. (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.