The automatic filling valve is a device consisting of a pressure reducing valve with compensating seat, visual system pressure setting indicator, an inlet filter, anti-scale internal parts, a shut-off valve (round knob on bottom) and a check valve. It is installed on the water inlet piping in sealed heating systems, and its main function is to maintain the pressure of the system at a set value, automatically filling up with water as required.

Caleffi Auto Fill Automatic Filling Valve with Pressure Setting Indicator, Series: 553, 1/2 in Nominal, Sweat x FNPT Connection, 230 lb/sq-in Inlet, 15 lb/sq-in Pressure Outlet, 3 - 60 lb/sq-in Range Pressure, Brass, 150 deg F, 4-3/4 in L x 5.937 in H

• Pre-adjustable, automatic filling valve
• Anti-scale with visual system pressure setting indicator
• Complete with manual shut-off valve, strainer and check valve

• Full Engineering Drawing https://assets.unilogcorp.com/267/ITEM/DOC/Caleffi_553549A_Full_Engineering_Drawing.pdf
• Instruction/Installation Manual https://assets.unilogcorp.com/267/ITEM/DOC/Caleffi_553549A_Instruction_Installation_Manual.pdf
• Specification Sheet https://assets.unilogcorp.com/267/ITEM/DOC/Caleffi_553549A_Specification_Sheet.pdf