Boiler Fill Valves & Feed Valves

A boiler fill valve (also called a boiler feed valve or pressure reducing valve) keeps a hydronic heating system at the right cold-fill pressure, usually 12 to 15 psi for a typical two-story home. It automatically adds make-up water when pressure drops and lets you fast-fill the system after service. If your boiler pressure keeps falling, the fill valve never shuts off, or the relief valve drips, a worn or clogged fill valve is a common cause.

This collection lists fill and feed valves by part number, including Caleffi AutoFill 553 and 573 series (with or without gauge, NPT, sweat and press connections), the Caleffi 573/574 COMBO models with a built-in backflow preventer, Resideo NK300S and FM911 feed valve and backflow combinations, and Taco 329 fast-fill and 335 boiler feed valves. Replacement cartridges are listed where available.

Many local codes require a backflow preventer on the boiler fill line. A combination valve saves space and two joints. Match the inlet and outlet size (1/2" or 3/4"), connection type and pressure range to your system, and check whether your boiler needs an ASSE 1012 or 1013 backflow device.

Shop the rest of the hydronic water side in Boiler Parts, or go straight to relief valves, expansion tanks, backflow preventers and system fill tanks.