Single Orifice Air Valve

Single Orifice Air Valve

The Single Orifice Air Valve — also known as a small orifice or automatic air release valve — continuously vents accumulated air from water and pipeline systems during normal operation. Made from high-quality ductile iron (GGG40/50), it handles working pressures up to 16 bar (25 bar optional) and is available from DN50 to DN300, with flanges drilled to EN1092-2.

Unlike a kinetic (large orifice) air valve, which is designed for high-volume air discharge during pipe filling and draining, the single orifice air valve is built for small, continuous air release while the system is under pressure — making it ideal for pump station outlets and water distribution mains.

Technical Specification

Item	Specification
Standard	EN1074-4, BS, ANSI
Type	Flanged type, or with brass isolation valve
Size Range	DN50 – DN300
Working Pressure	10 bar / 16 bar / 25 bar
Shell Test Pressure	15 bar / 24 bar / 37.5 bar
Seal Test Pressure	11 bar / 17.6 bar / 27.5 bar
Body Material	Ductile iron GGG40/50, Cast Iron GG25, or Carbon Steel
Float Ball	SS304, ABS, or NBR
Coating	Fusion bonded epoxy coating (internal & external), min. 250μm, or liquid epoxy painting
Max. Working Temperature	100°C
Flange Standard	Drilled to EN1092-2 (BS4504)

Key Features

Continuous, automatic air release under system pressure — no manual operation required

Single-direction airflow control with reliable sealing design

Maximum working pressure of 16 bar (25 bar optional)

Float moves in a fixed path without contacting the valve shell, extending service life

Compact, low-profile design — shorter overall height than comparable air valves

Compatible with a range of gases and liquids

Ductile iron construction for long-term durability and low maintenance

Manufactured to EN1074-4, BS, and ANSI standards

Choosing the Right Material

Body material:

• Ductile iron GGG40/50 — the standard choice for most water and pipeline applications, offering strong mechanical performance and good corrosion resistance

• Cast iron GG25 — a more economical option for lower-pressure, less demanding environments

• Carbon steel — used where project specifications call for higher pressure ratings or specific material standards

Float ball material:

• SS304 — general-purpose and durable, suitable for most water and mild chemical environments

• ABS — a lightweight, cost-effective option

• NBR — offers better resistance where oil or chemical compatibility is a concern

If you're not sure which combination fits your media and operating conditions, let us know your application and we'll recommend a configuration.

Single Orifice vs. Double Orifice vs. Triple Function Air Valve

Not sure which type fits your project? Send us your pipeline working pressure, elevation profile, and flow rate, and our engineers will recommend the right valve type and size.

How It Works

When air enters the valve from the pipeline, it displaces water inside the chamber, causing the float to drop. This allows the trapped air to escape through a small orifice, maintaining efficient system performance. Once the air is vented, the float rises again and reseals the orifice.

If the pipeline develops negative pressure, the float drops rapidly and the valve admits air into the line, protecting the pipeline from vacuum-induced collapse.

Note: This model is not suitable for sewage pipelines. For sewage or wastewater applications, please contact us for a suitable alternative.

Typical Applications & Industries

• Municipal water supply and distribution networks

• Treated water lines in wastewater treatment plants (see FAQ regarding raw sewage)

• Irrigation and agricultural water systems

• Mining and industrial dewatering pipelines

• Power plant cooling water systems

• Compressed air and pneumatic systems

• Gas pipelines

• Pump station outlets and elevated pipeline sections

• Water towers and reservoirs

Three functions

1, large amount of air releasing (main vent )
2, small amount of air releasing (small vent overriding)
3, rapid air filling 

It allows air to escape when filling the pipe.
It allows air to enter when emptying the pipe (preventing pipe collapse)
It allows continuous automatic control, eliminating accumulated air, even when the system is under pressure.

Frequently Asked Questions

Q:Where should a single orifice air valve be installed?

It is typically installed at pipeline high points and at pump station outlets, where air naturally accumulates due to its lower density compared to the fluid. Installing the valve at these points prevents airlocks that can restrict flow and increase operating costs.

Q:Can a single orifice air valve be used in sewage pipelines?

No. This model is not designed for raw sewage or wastewater applications. Please contact our engineering team for a suitable alternative for sewage systems.

Q:What sizes and pressure ratings are available?

The valve is available from DN50 to DN300, with working pressure ratings of 10 bar, 16 bar, or 25 bar, depending on your system requirements.

Q:What standards does this valve comply with?

The single orifice air valve is manufactured to EN1074-4, BS, and ANSI standards, with flanges drilled to EN1092-2 (BS4504).

Q:How do I choose between ductile iron, cast iron, and carbon steel body material?

Ductile iron GGG40/50 is the standard choice for most water applications. Cast iron GG25 is a more economical option for lower-pressure, less demanding environments. Carbon steel is used where project specifications require higher pressure ratings or specific material standards. Contact us with your application details and we can recommend the right material.

What information do I need to provide for a quote?

Please provide the nominal size (DN), working pressure, applicable standard, body and float material preferences, connection type, operating medium, and quantity. See the "How to Request a Quote" section above for the full list.