Section 435.11 - Pool Slopes and Dimensions(1) The minimum depth of water in swimming pools to be used for swimming purposes shall be not less than three feet. In any part of the pool less than five feet in depth, slopes in the pool floor shall remain constant and shall not exceed one foot vertical in 12 feet horizontal. Exception may be made by the Board of Health for pools built principally for instruction, or in a recessed area of the main swimming pool where the pool is of any irregular shape, such as the leg of a "T", "L", or "Z".(2) In special purpose pools the maximum operational water depth shall be four feet measured from the waterline. The maximum depth of any seat or bench shall be two feet measured from the waterline.(3) Walls of swimming pools shall be vertical or shall have a maximum vertical slope of one foot horizontal to five feet vertical. Where pools are used for competitive swimming the walls shall be vertical for a minimum water depth of three feet six inches. When coved construction is used to join the walls and bottom of any pool the following shall apply: (a) At depths of from three feet to four feet six inches, the maximum radius of coving shall be 12 inches.(b) At depths greater than four feet six inches, the radius of coving joining the wall and floor at any point shall be equal to not more than the depth of the pool at that point minus two feet six inches. No ledges or any other abrupt change in the wall slope shall be allowed except for reasonable fillets or coving where the wall joins the pool bottom. Plane surfaces tangent to allowable coving may be used in lieu of curves.(4) Notwithstanding the provisions of 105 CMR 435.11(3), a safety ledge not more than four inches in width and located about four feet six inches below the pool water surface may be permitted, provided it is sloped slightly toward the center of the pool to prevent dirt accumulation.