This is a 24 volt, AC electrically-operated valve that turns the water on and off to your humidifier. Preinstalled inside of the valve is a strainer screen, which filters the water before it passes through the valve, catching things like sand and dirt which could otherwise cause blockage. This valve needs to be replaced about every ten years, or more often if it fails and is stuck open or closed. Fits models 1040L, 1040LH, 709L, 709LH, 1040, 1042L, 1042LH, 1137, 1042DM, 1042DME. GeneralAire® Solenoid Valve, For Use With: GeneralAire® Humidifier Model 1040 and 1137, 1/4 in ID x 1/2 in OD Inlet, 1/4 in ID x 1/2 in OD Outlet, 3/32 Orifice, 24 V, 2.5 W, 2-Wire, 3-1/4 in L