The Apollo™ Model DC4A and DCLF4A Lead Free Double Check Valves A Series prevent contamination of the potable water supply due to back-siphonage or backpressure from substances that are objectionable to the potable water supply, but non-health hazards. The top accessed modular check valve cartridges provide captured springs, replaceable seats and reversible silicone seat discs. This Made in America assembly features ball valve shutoffs with stainless steel handles and nuts as standard and carries the five-year Apollo™ factory warranty.