S.C. Code Ann. § 46-1-140

Any irrigation system which is designed or used for the applications of fertilizer, pesticide, or chemicals must be equipped with an anti-syphon device adequate to protect against contamination of the water supply. The minimum acceptable anti-syphon device shall include a check valve, vacuum breaker, and low pressure drain on the irrigation supply line between the irrigation pump and the point of injection of fertilizer, pesticide, or chemicals. The vacuum breaker must be upstream from the check valve. The low pressure drain must be upstream from the vacuum breaker. The injection pump must be tied to the irrigation pump either mechanically or electrically so that the injection pump shall stop operating if the irrigation pump fails to function. Any person who uses an irrigation system for the application of fertilizer, pesticide, or chemicals which is not equipped with an anti-syphon device as required by this section is subject to a civil penalty of not more than five hundred dollars. Each day's violation is subject to an additional fine. The Division of Regulatory and Public Service Programs at Clemson University shall promulgate regulations with the advice of the Department of Health and Environmental Control as it considers necessary to implement this section and is also charged with enforcing this section. The provisions of this section do not apply to residential yard use.