An air valve controls how air enters or leaves irrigation piping. To choose the right type, identify when the problem occurs. An automatic air-release valve releases accumulated air while the system is under pressure. A kinetic air/vacuum valve works during filling and draining. A combination valve covers all three situations. Location and size depend on how each section fills, operates and drains.
Why air in pipes is a problem
During filling, the air that was already in the tube needs to escape. With irrigation in operation, part of the air dissolved in the water can be released, for example, when the pressure drops. If there is an entry path and internal pressure below atmospheric, air can also enter through joints or connections. Air pockets tend to accumulate at high points in the piping and can restrict the passage of water, increase pressure loss and impair the functioning of meters and control valves. AVK, air in water pipes
In drainage, if the water leaves faster than the air can enter, the pressure can drop below atmospheric pressure. This condition can deform susceptible pipes and pull soil particles into drippers. Embrapa describes the entry of particles through the emitter at the end of irrigation. If the problem is recurring, also check other causes of dripper clogging. Embrapa, Documents 182
Types of air valves and what each one does
Automatic air-release valve (small orifice)
It releases small quantities of air that accumulate while the system is under pressure. Its release capacity depends on the pressure and model. Use the kinetic function where large volumes of air need to enter or escape.
Kinetic air/vacuum valve (large orifice)
The larger orifice lets air out as water fills the pipe and admits air as the system drains. In air/vacuum models, the float closes the orifice when water reaches the valve. The automatic orifice, if present, releases air pockets while the line is under pressure. Bermad, K10 kinetic air valve
Combination air valve
It combines the kinetic and automatic functions. Some versions restrict air discharge near the end of filling to reduce the impact of valve closure. Choose this option based on the system's hydraulic behavior. Bermad, C10 technical sheet
| Type | Filling | Pressurized operation | Drainage |
|---|---|---|---|
| Automatic | Outside its intended function | Releases accumulated air | Outside its intended function |
| Kinetic | Exhausts large volumes of air | Outside its intended function | Admits air |
| Combination | Exhausts large volumes of air | Releases accumulated air | Admits air |
Catalogs may count functions in different ways. Check the data sheet to see whether the model admits air during draining, exhausts it during filling and releases it under pressure.
Where to install air valves in an irrigation system
The designer checks the pipeline profile against the locations of pumps, valves, discharge points and emitters. Use the locations below to review the layout. Hydraulic calculations determine where air valves are needed, what each one must do and the required capacity.
On supply pipelines and mainlines
Check high points where air tends to accumulate, and sections where operating changes may cause drainage. Bermad lists high points, supply lines and pipe sections downstream of pumps among the applications for its combination air valve. Check changes in slope and long runs when reviewing the profile. Assess the position near the pump together with the check valve and the startup and shutdown sequence. Bermad, C10 applications
If you are checking the network operating conditions, see how to choose the pump for irrigation.
At the control headworks
At the filtration and fertigation station and downstream of main valves, check whether the layout creates sections that fill or drain separately. The C10 data sheet lists these as application points. Consider what happens when the pump stops or the control valves change position. Bermad, C10 applications
In the irrigation zone
After the zone valve closes, water may continue flowing through the emitters. If pressure falls below atmospheric pressure, a valve with air intake helps protect that pipe section. One layout the manufacturer describes places the valve at the high points of the distribution line, downstream of the zone valve. The C10 data sheet also lists applications near water meters and automatic regulators. Bermad, protecting the irrigation zone against vacuum
Subsurface drip irrigation needs extra attention
In subsurface drip irrigation, the emitter outlet is in contact with soil. Embrapa advises paying closer attention to vacuum protection in subsurface plots than in surface drip systems because drainage can draw particles into emitters. Anti-siphon emitters are an additional measure to consider. Select emitters and air intake points as part of the same design. Embrapa, Documents 65 · Rivulis, entry of soil particles
How to size an air valve
The thread tells you how the valve connects. Use the model's flow curves to assess its air discharge and intake capacity. Before asking for a specification or comparing quotes, gather four pieces of information.
- Profile and diameters. Mark the high points, drainage points and valve positions on the layout.
- Filling. Provide the expected flow rate and identify which sections will fill during each operation.
- Drainage. Identify where water exits and under what conditions, such as after a zone valve closes or during a planned flush.
- Pressures. Provide the operating pressure. Check the data sheet for the minimum sealing pressure and air intake capacity at the allowable vacuum for that section.
Where a line drains through its emitters, assess the air intake capacity under those conditions. Air valves with the same connection size can perform differently. Compare the intake and discharge curves across the design pressure range and confirm the selected model. Bermad, air valve selection and measured flow curves · Bermad, protecting the irrigation zone against vacuum
Installation precautions
Follow the manufacturer's manual and leave room for inspection. Bermad's installation guide recommends mounting the air valve vertically and fitting a full-bore isolation valve upstream. If there is a riser, check its inside diameter. The guide recommends an opening at least as large as the air valve orifice. Avoid reductions that limit air flow, especially during draining.
Consider an air collection chamber for sections that fill and drain frequently. Choose a location where discharged water can be directed away and the air opening is protected from flooding and dirt. Bermad, air valve installation · AVK, installation on water pipes
Maintenance: what to check
During filling, some models may discharge a little water before the float seals. If water continues escaping after the system stabilizes, have the team check the float and seals for debris and confirm that pressure is within the model's operating range.
Before opening the air valve, isolate and depressurize the line section or valve body as directed by the manufacturer. After inspection, check that the isolation valve is back in its operating position and observe what happens during the next operating cycle. Include this check in the system maintenance plan. Bermad, C10 inspection and cleaning
FAQ
What is the difference between an air valve and a pressure relief valve?
An air valve controls the flow of air. A pressure relief valve discharges water when pressure exceeds its set point. Protecting the system may require both functions. Bermad, pressure relief in irrigation
Does an air valve prevent water hammer?
An air valve can help manage air involved in sudden pressure changes. Rapid closure of the air valve itself can also generate a pressure surge. When determining protection, assess pump starts and stops, valve closure and the speed at which the pipe fills. Bermad, pressure surges in irrigation systems
Does drip irrigation on flat ground need an air valve?
It may. Even on relatively flat ground, drainage through the emitters after the zone valve closes can lower pressure in the line. Whether air valves are needed, and how many, depends on the pipe profile and how the zone fills and drains. Bermad, protecting the irrigation zone against vacuum
Conclusion
Start with how the system behaves. If the problem occurs at startup, check how air leaves as the line fills. If it occurs under pressure, look for places where air can accumulate. If it occurs at shutdown, check where water drains and whether air has enough room to enter.
To talk to Perin about a drip design, provide the municipality, crop, approximate area and water source. For an existing system, add the piping layout and explain which operation triggers the problem. Contact the team on WhatsApp (14) 99824-5219 or by email at contato@perinirrigacao.com.br.
Sources consulted
Research conducted on November 6, 2026.
- AVK Válvulas do Brasil. Why use air valves in water and wastewater applications.
- Bermad. C10 Combination Air Valve. Technical sheet.
- Bermad. K10 Kinetic Air Valve.
- Bermad. Protect Your Plot Irrigation System from Vacuum Conditions.
- Bermad. How to Install an Air Release Valve in an Irrigation Pipeline.
- Bermad. How to Service and Clean a Bermad C10 Air Release Valve.
- Bermad. Optimal Air Valve Selection for Water Systems.
- Bermad. How to Minimize Water Hammer in Irrigation Schemes.
- Bermad. Pressure Sustaining, Circulation and Relief in Irrigation Systems.
- Albuquerque, P. E. P. and Maeno, P. Crop water requirements for sizing and managing localized irrigation systems. Embrapa Milho e Sorgo, Documents 65, 2007.
- Almeida, O. A. Emitter clogging in localized irrigation. Embrapa Mandioca e Fruticultura Tropical, Documents 182, 2009.
- Rivulis. Clogging Cause – Soil Ingestion.
