SPECIAL ORDER ITEM. Review Returns Policy before purchase. The A.Y. MCDONALD Dual Check Valve is engineered to provide reliable backflow prevention in potable water systems. Designed for inline installation, it features 2 independently operating check valves for enhanced protection. The accessible body design allows for easier inspection and servicing without complete removal from the line. Its durable, corrosion-resistant construction ensures long-term performance in demanding water service applications.