Air Vents and Vacuum Breakers

Essential devices for proper functioning of heating and hydraulic systems. They eliminate trapped air, prevent corrosion, avoid noise and circulation blockages. They protect pipework from collapse during draining.

Why eliminate air from systems

Air is the invisible enemy of hydraulic and heating systems. It enters during filling, is released from heated water (gas solubility decreases with temperature) and penetrates through permeable components. Once in the system, air causes annoying noise (gurgling, water hammer), reduced thermal efficiency (air pockets in heat exchangers), accelerated corrosion (oxygen attacks ferrous metals) and in worst cases complete circulation blockage (airlock).

Automatic air vents solve these problems by continuously expelling air that accumulates at high points. Vacuum breakers perform the complementary function: they allow air to enter when a vacuum develops (during draining or rapid cooling), preventing pipe collapse and facilitating drainage.

Roffia distributes a complete range of air vents, vacuum breakers and air separators from Caleffi and Spirax Sarco, for civil and industrial systems up to steam applications.

Air vents and vacuum breakers — Roffia srl

Automatic air vents

  • Internal float opens/closes vent
  • Fully automatic operation
  • Body in brass, steel or stainless steel
  • DN 10–25 (½"–1"), PN 10–16
  • Temperature up to 110 °C (standard)
  • High-temperature versions for steam

Vacuum breakers

  • Prevents pipe collapse under vacuum
  • Facilitates circuit draining
  • Combined with air vent (dual function)
  • Essential on heat exchangers and tanks
  • Body in brass or stainless steel
  • DN 15–50

Air separators (de-aerators)

  • Remove dissolved air and microbubbles
  • Body with coalescence elements
  • Integrated automatic vent
  • DN 20–150, in-line installation
  • Reduce corrosion and cavitation
  • For efficient heating systems

Air vents for steam systems

  • Thermostatic vents — expel cold air at start-up
  • For steam lines — steel or stainless body, high temperature
  • For heat exchangers — prevent air pockets in tube bundle
  • Brands: Spirax Sarco, ARI, Gestra
  • Essential for steam system efficiency

Manual bleed valves

  • Bleed cocks — for radiators and terminals
  • Handwheel valves — manual air discharge in plant room
  • Bleed keys — accessory for radiator venting
  • Economical, but require manual intervention
  • Complement automatic vents at terminal points

Typical applications

Heating systems

Automatic air vents at the top of each riser, on boilers and cylinders, at headers and heat exchangers. Air separators on the primary circuit (hot side, after boiler) remove air released by heating before it reaches terminals. Result: always-hot radiators, no gurgling, reduced corrosion.

Chilled water circuits

Chilled water circuits also suffer from trapped air. Air vents at high points and separators in the plant room ensure maximum efficiency of fan coils and cooling coils. Vacuum breakers prevent collapse during seasonal draining.

Steam distribution networks

At start-up of a steam system, the lines are full of cold air that must be expelled before steam can reach them. Thermostatic (thermal) air vents open while cold air exits and close automatically when hot steam arrives. Installation: high points, line ends, heat exchanger inlets.

Tanks and vessels

Vacuum breakers are essential on tanks, autoclaves and shell-and-tube heat exchangers. During rapid draining or cooling, internal vacuum could cause structural collapse. The vacuum breaker allows air in, equalising pressure and avoiding costly damage.

Roffia air vent and vacuum breaker range

Automatic vents
Brass and stainless, DN 10–25
High temperature
For circuits up to 150 °C
For steam
Thermostatic Spirax Sarco
Vacuum breakers
Single and combined
Air separators
Caleffi Discal, DN 20–150
De-aerators
For critical circuits
Manual valves
Bleed cocks, handwheel
Accessories
Isolation valves, caps

Frequently asked questions

What is the difference between an air vent, a bleed valve and a vacuum breaker?
An air vent (or automatic air eliminator) is used to expel air and non-condensable gases that accumulate at high points in the system during normal operation. It is always connected to atmosphere and opens automatically when air accumulates. A bleed valve is a generic term that can refer to either automatic air vents or manual bleed valves (handwheel cocks). A vacuum breaker has the opposite function: it allows air to enter when a vacuum develops in the circuit (e.g. during draining), preventing pipe collapse and facilitating drainage. Often an air vent and vacuum breaker are combined in a single dual-function device.
Why is air in the system a problem?
Air and non-condensable gases cause multiple problems: (1) Reduced heat transfer — air pockets in heat exchangers and radiators prevent fluid from reaching heat transfer surfaces; (2) Noise — gurgling, water hammer, vibrations in pipework; (3) Corrosion — dissolved oxygen causes internal corrosion of steel pipes and components; (4) Cavitation — air micro-bubbles promote cavitation erosion in pumps; (5) Flow blockage — large air pockets can completely block circulation (airlock). Automatic air vents prevent these problems by continuously removing air released from the fluid.
Where should air eliminators be installed?
Air eliminators should be installed at all high points in the system where air tends to accumulate: (1) Top of risers in heating systems; (2) High points of heat exchangers and boilers; (3) After pumps (air released by cavitation rises immediately); (4) Centralised air separators on the primary circuit; (5) Terminals such as radiators and fan coils (automatic or manual bleed valves). For steam systems, air vents should be positioned at start-up to expel cold air before steam arrives.
What is an air separator and when is it needed?
An air separator (or de-aerator, microbubble separator) is a device that actively removes dissolved air and microbubbles from the circuit water, not just expelling already separated air. It works by slowing the flow in a chamber with coalescence elements (meshes, rings) that encourage small bubbles to merge into larger ones, which then rise and exit through the top vent. Separators are recommended for medium-to-large heating systems, circuits with powerful pumps, and wherever minimising corrosion and maximising heat exchange efficiency is required. Roffia supplies Caleffi and other leading brand separators.
How often should an automatic air vent be checked?
Automatic float-type air vents are simple and reliable devices, but require annual verification: check for water leaks from the cap, manually verify that the mechanism moves freely (by pressing the manual bleed button if present), clean any limescale deposits. If the vent leaks water or no longer discharges air, the float or seal may be damaged — replacement is recommended. In systems with very hard or untreated water, more frequent maintenance may be necessary. Roffia supplies replacement air vents and seal kits.

Request a quote for air vents and vacuum breakers

Please provide system type, operating temperature and pressure. We will recommend the correct device — air vent, vacuum breaker or separator — with a prompt quotation.

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