The Weil McLain 640-000-026 T1-T2 Flowmeter is a precision flow-measuring component designed for use with Weil McLain wall-mounted boilers and hydronic heating systems. It monitors water movement between the T1 supply and T2 return connections, providing flow information to the boiler control system. The flowmeter detects water movement and converts it into an electrical signal for ac... https://www.partshnc.com/640-000-026-weil-mclain-flowmeter-t1-t2-wall-boiler