Purger

A steam vent is the device that releases trapped air from a hydraulic system (heating, chilled water, recirculated domestic hot water). Air bubbles and pockets create noise, restrict flow, distort measurements, and degrade the temperature difference (excessively hot return water, lukewarm emitters). A properly installed and maintained steam vent restores continuous circulation, stabilizes regulation, and protects pumps, heat exchangers, and valves. It should not be confused with a steam condensate vent (for steam systems) or the condensate drain from air conditioning units.

Purger: definition, types and implementation

- Manual bleeder (needle valve, bleed screw): simple, economical; to be operated during filling and restarting.

- Automatic air vent (float): continuously evacuates air; is placed at high points, on air separators, collectors, column heads and equipment (tanks, exchangers).

- Air/microbubble separator : specific housing that captures circulating microbubbles; very effective on variable flow networks.

- Key accessories : isolation valve under automatic vent (for maintenance), anti-leak plug, correct fittings to avoid air intake.

Installation rules

- Install at high points and changes in slope, on collectors and at the top of the column; provide drainage at low points.

- Near boilers/heat pumps/heat exchangers, place an air separator on the hot return (air solubility ↓ with temperature).

- Provide isolation and accessibility (hatch, height); avoid locations subject to water hammer.

- On closed-loop DHW systems, use purges adapted to the sanitary water (materials, hygiene).

Advantages, limitations, and points to consider when using a well-managed purger

Interests

• Comfort & silence: disappearance of gurgling and whistling noises.
• Performance: ΔT restored, heat pump/boiler efficiency ↑, defrosting/cycles ↓.
• Protection: pumps, heat exchangers and valves under less stress; limited corrosion (dissolved oxygen ↓).

Boundaries

• An automatic air vent without isolation = difficult maintenance.
• Sludge/particles can block float/seat; a poorly placed bleeder valve can suck in air.
• Does not correct a structural air leak (depression, cavitation, defective seals).

Points to consider

• Before filling with water: descaling, rinsing, methodical purging from bottom to top.
• Water quality: corrosion inhibitor, controlled conductivity; combine with air/sludge separator.
• Hydraulics: reasonable speeds and ΔP to avoid cavitation/air suction; respect for speeds in the columns.
• Maintenance: regular check, replacement of seals/float if leaking; check the cap of the automatic bleeders.
• GTB/Operations: monitor ΔT and complaints; seasonal flushing after work on networks.

Anecdote — “The radiators are finally silent in Annecy”

In Annecy, an office building suffered from wind noise and cold spots during the shoulder seasons. The diagnosis: no air vents at the top of two risers, no air separator, and the system had never been flushed. The renovation included adding automatic air vents with isolation valves at the top of the risers, a microbubble separator on the boiler return line, and a complete flush. The result: quiet operation, the temperature difference (ΔT) returned to the setpoint, and a condensing boiler that is now condensing most of the time.