5 Colo. Code Regs. § 1003-5-3.15
All potable pool makeup water shall be introduced through a reduced pressure principle backflow preventer (RP) accepted by the Colorado Department of Health, Water Quality Control Division or fill spout with an air gap at least twice the diameter of the fill pipe. The pool fill spout shall be located under a low diving board or adjacent to a handrail and not extrude past the edge of the pool more than 1-1/2 times the diameter of the pipe. Water pressure shall be such so as to allow the fill line to operate at full valving and not interfere with water pressure in the other parts of the facility.
All other accessories to the recirculation system, such as chemical solution feeders and water fed chlorinators shall be protected against backflow into the water supply system by installation of an approved reduced pressure principle backflow preventer. The backflow preventer must be tested on installation and at least annually thereafter by a certified cross-connection control technician.
5 CCR 1003-5-3.15