The NTI Boiler 64980859 3-Way Valve System Group is a replacement valve assembly designed for compatible NTI boiler systems. It regulates water flow between heating and domestic hot water circuits, directing flow as required to maintain proper system operation. The valve system is commonly used in hydronic boilers and combination heating applications. Its reliable flow control support... https://www.partshnc.com/nti-boiler-64980859-3-way-valve-system-group