Watts Water Technologies FV-4M1 Automatic Float Vent

The Watts FV-4M1 Automatic Float Vent is a 1/4 in, male NPT threaded air vent designed to continuously remove trapped air from hot or cold water hydronic systems while preventing water loss. Its brass body and cover house a high‑temperature resistant polyethylene float and a silicone rubber seal, and the valve operates vertically to automatically vent air and reseal, also serving as an anti‑vacuum device when systems are drained. Rated for up to 150 psi (10 bar) and a minimum working pressure of 1.45 psi (10 kPa), with a temperature range of 33°F to 240°F (5°C to 116°C), it is glycol compatible and suitable for boilers, hydronic heating, radiant floor heating, chilled water systems, heat exchangers, circulation loops, and other HVAC installations. The FV-4M1 is disassemblable for inspection and cleaning and is commonly used in residential and commercial hydronic heating and water distribution systems; common replacements include Watts FV-4M1-1/8, FV-4M1-1/2, and FV-4M1-3/4.