Air Valves in Water and Wastewater Applications

Air is present in all water and wastewater pipelines. Therefore, safe and efficient operation requires continuous removal of air. Air valves in water applications contribute to smooth flow in pipelines and reduce maintenance and replacement costs.

All water supply systems consist of pipes that transport water from its source to its destination. In the process, pockets of trapped air can form in the pipelines. Air and wastewater gas pockets are difficult to detect and will reduce the overall efficiency of the piping system. The Air pockets can also cause water hammer problems, complete stoppage of flow, pipe bursting, system noise, and pipe corrosion. Air in the pipeline can also cause unstable operation of control valves, meters, and equipment. To ensure safe and efficient operation, it is essential to remove air and wastewater gases from the water system continuously.

What Causes Air in Water Pipes?

Air and vacuums formed in water main pipelines can lead to serious operational problems and even some serious consequences. Air can enter piping systems in several ways:

Empty Pipelines

Improved pipelines are filled with air. Most of it is evacuated during start-up, but some air pockets can remain in the system.

Air in the Liquid

Depending on temperature and pressure, liquids such as water can contain trapped or dissolved air. As the liquid flows, it separates from the liquid and can become trapped at high points in the system. Also, in pipelines that transport wastewater, the liquid waste can undergo chemical reactions and evolve into gases that can become trapped in the wastewater system.

Mechanical Equipment

Air can also enter a pipeline through mechanical systems such as pumps, pipe joints, valves, etc. Leaks or faulty seals in these components can cause air to leak into the piping system.

Advantages of Using Air Valves in Water Applications

Therefore, one solution to preventing contamination is to remove one of three issues: The driving force. Air valves are the most efficient and cost-effective tool to achieve this and by installing and maintaining an air valve system, negative pressure is managed and removed from the equation, allowing even old networks to remain protected from contamination from soil.

A vacuum in a pressurized piping system can be caused by ineffective air valves that do not respond to hydraulic conditions, failure of air valves due to lack of maintenance, or the absence of air valves in the pipeline altogether.

Air valves are often associated with removing air from a system and are therefore commonly known as air release valves. However, this name is misleading as their function of introducing air into the system to avoid a vacuum is just as important.

Video explaining how air valves work in water applications

What are the consequences of air and voids in pipelines?

Air and voids formed in a pipeline can have serious effects on the operation of a pipeline. Some of these effects include:

• Reduced pumping efficiency: Air in pipelines can reduce the efficiency of a pumping system. Air trapped at high points in the system inhibits flow, increasing the head pressure and therefore the energy required to create flow.
• Pipe corrosion: Depending on the temperature of the pipeline, the oxygen in trapped air can be a strong corrosive agent. Oxygen gradually oxidizes the metal, leading to rust, blockages, and structural failure of the pipe.
• Faulty measuring and measuring devices: Air pockets and voids can cause problems for flow measuring and controlling devices. They affect the devices’ ability to accurately measure and control flow.
• Air hammer: When a pocket of air is trapped in a pipe, pressure builds up around the blockage. The pressure of the water circulating around this blockage sends vibrations throughout the pipe. This vibration, known as air hammer, can damage critical installations.
• Pipe Failure: Voids can cause catastrophic failures in pipelines. If there is a large void, the pipe can collapse inward due to the pressure difference on either side of the pipe walls.
• Corrugated Pipes

The Function of Air Valves in Water and Wastewater Applications

Air valves are hydromechanical devices with an internal float mechanism designed to release trapped air and wastewater gases during the filling and operation of a piping system.

They also ensure that air is inlet during drainage to maintain positive pressure. This is important because negative pressure creates a vacuum that can cause pipes to collapse and introduce contaminants into the system.

Therefore, air valves provide protection against transient pressures and trapped air in pipelines, which are the main causes of pipeline bursts, collapses, and cracks.

With the correct use of air valves, you will achieve:

• Reduced energy consumption and operating costs
• Reduced pressure loss
• Reduced delay when filling the piping system
• Reduced risk of water hammer
• Reduced failure or inaccuracy in flow measurement
• Reduced corrosion
• Reduced risk of contamination
• Reduced risk of pipe bursting and collapse
• Reduced replacement costs
• Reduced consumption due to the increased life of the network
• Reduced pump capacity is required due to reduced head loss

Three Main Types of Air Valves

There are three types of air valves installed in water systems: automatic air valves, air and vacuum valves, and combination air valves.

Automatic air valves continuously release relatively small amounts of air from a pressurized line. Automatic air valves are also known as small orifice air valves and compressed air valves.

Air and vacuum valves release large amounts of air when filling a pipeline. Vacuum and Air valves allow large amounts of air to be introduced when lines are drained or air and vacuum valves are kinetic air valves, large orifice air valves, vacuum breakers, low-pressure air valves, air relief valves, and single-acting air valves.

Air valves combine the functions of automatic air valves and air and vacuum valves. The automatic air release function releases accumulated air from the system while it is under pressure, and the air and vacuum function discharges and accepts large amounts of air while filling or draining pipelines. Air valves are also known as double-acting air valves, double-acting air valves, and double-acting air valves.

You can find more technical details for all types of valves that we offer at CareWater.

Air Valve Size and Location

Air valves are sized for a specific installation taking into account the flow, location, and performance of the air valve. Therefore, the natural diameter of the air valve is not equal to the natural diameter of the pipe it is installed on. The size and location of air valves for a specific project are determined by advanced calculation programs that provide analyses such as fill rate analysis, drainage analysis, burst analysis, water column separation analysis, and energy-saving analysis.

The primary function of an air valve is to remove unwanted air pockets from a pipeline. However, it only works effectively when it is installed correctly. Proper location of the air valve can significantly improve water flow performance. Therefore, air valves should be installed at those points where the pipeline is most exposed to vacuum conditions. In general, the optimal installation of the air valve is at the peak of the pipeline, and the valve should always be installed vertically.

Before installing the air valve, the location should be considered so that the valve is protected from freezing, contamination, and flooding. The air valve should be easily accessible to allow for maintenance, operation, and inspection.