Air Release Valves 101: Protecting Your System from Pressure Surges and Inefficiency

In pressurized piping systems, air release valves play an essential role in maintaining smooth, efficient operation and protecting equipment from damage. Below is a refined, more technical overview to help you understand when, why, and how to use them — plus tips for sizing, placement, and maintenance.

Why You Need Air Release Valves

Trapped air in pipelines is more than just an annoyance — it causes a host of problems:

• Flow disruption & head loss: Air collects at high points, blocking or restricting fluid flow, forcing pumps to work harder.
• Pressure surges / water hammer: When air pockets suddenly move or collapse, a high-pressure shock can propagate through the system, damaging pipes, valves, and instrumentation.
• Instrument & pump errors: Air in lines can lead to inaccurate pressure or flow readings, pump cavitation, and surges in power draw.
• Corrosion & maintenance issues: Oxygen-rich air pockets accelerate corrosion, especially in metal piping systems.
  
  

Air gets into a system from several sources:

• Initial filling — Before fluid enters, the pipe is filled with air.
• Dissolved gases — Fluids like water carry dissolved air, which can evolve out into bubbles under pressure or temperature changes.
• Leaks or permeation — Through seals, joints, valves, or small leaks, air can be drawn into the system during operation.

So the goal is clear: continuously and automatically remove collected air to maintain system integrity. Valves such as the Val-Matic Clean Water Air Release Valve and Val-Matic Wastewater Air Release Valve are specifically designed to perform this function reliably in both clean and dirty service conditions.

How Air Release Valves Work

An automatic air release valve is simple in principle:

• It's installed at a system’s high point(s) (where air naturally collects).
• As air accumulates inside, it displaces liquid and lowers the liquid level inside the valve body.
• A float drops as the liquid level drops, opening the valve and venting the air to the atmosphere.
• Once the air is expelled, liquid re-enters, the float rises, and it seals off again.
  
  

This cycle repeats continuously. Key design considerations:

• The inlet port of the valve should face downward to allow air to accumulate in the air release valve.
• A shut-off or isolation valve should always be installed beneath the air release valve so it can be serviced without shutting down the entire line.
• Outlet connection and manhole vent should be configured to avoid backflow, water column formation, or freezing (in cold climates).
• Flush connections or core exchanges for easy maintenance.
  
  

Products like the Val-Matic Clean Water Air Release Valve are ideal for potable or process water applications, offering precision venting and corrosion-resistant materials. For more demanding conditions such as wastewater or sludge lines, the Val-Matic Wastewater Air Release Valve is engineered with large orifice designs and anti-clog features to handle solids effectively.

Where & When to Use Them

Air release valves are best for closed, pressurized systems where small or moderate volumes of air need to be vented. Typical use cases include:

• Water distribution lines
• Sewer force mains
• Industrial fluid circuits
• Closed-loop heating or cooling systems
  
  

Because the orifices are relatively small, they’re ideal when air volumes are moderate. For large-volume venting — e.g. during filling or rapid drainage — you may want to pair them with air/vacuum valves or combination air valves that handle both intake and exhaust in large flow conditions.

For example, the Val-Matic Clean Water Air Release Valve can be placed at system high points to prevent air locking in municipal or industrial water lines, while the Val-Matic Wastewater Air Release Valve is well suited for sewer force mains or any system carrying solids-laden fluids.

Benefits & Limitations

Advantages

• Constant, automatic operation — no manual intervention needed once installed.
• Protection from damaging pressure surges.
• Improved hydraulic performance and energy efficiency.
• Prevents air binding or flow stoppage.
  
  

Limitations & Cautions

• If the system has extremely fast flow changes (filling/draining), the valve may not vent fast enough — sizing becomes critical.
• The valve must be sized appropriately for the maximum expected air flow demands.
• In cold climates, venting can allow freezing of small amounts of liquid in the valve headers — insulation or heat tracing may be needed.
• Sediment, scale, or debris in fluid can foul the float mechanism or valve seat — good filtration upstream is advised.
  
  

The Val-Matic Wastewater Air Release Valve includes design features that minimize fouling and allow for easier maintenance, while the Val-Matic Clean Water Air Release Valve provides a high-performance option for systems where clean, corrosion-free service is essential.

Sizing & Selection Tips

To get the right air release valve:

• Estimate the maximum volumetric flow rate of air needing venting (for instance when purging or startup).
• Consult manufacturer curves for orifice capacity vs. pressure differential.
• Choose materials compatible with your fluid (e.g. stainless, brass, plastic) and protective coatings or seals for corrosive environments.
• Confirm the valve’s pressure rating, temperature range, and maintenance accessibility.
  
  

For most water and wastewater applications, Crane Engineering recommends the Val-Matic Clean Water or Wastewater Air Release Valves, depending on the fluid medium and solids content.

Installation & Maintenance Best Practices

• Install the valve at the highest possible point in the line where air accumulates (may include multiple air release valves in a line).
• Maintain vertical orientation, with the inlet downward.
• Provide a dedicated access route and isolation valve for service.
• If the valve vents above ground, route vent piping or mufflers to avoid noise or aerosol spray.
• Schedule periodic inspections: check for leakage, proper cycling, float movement, and clean the orifice or seat if needed.
• Consider redundancy in critical systems (dual valves or backup) to avoid a single point of failure.
  
  

Both Val-Matic Clean Water and Wastewater Air Release Valves are designed for straightforward maintenance with easy access to internal components and long-lasting float mechanisms, reducing downtime and service costs.

Final Thoughts from the Field

Trapped air in piping systems is a silent threat to performance, reliability, and safety. Installed properly, automatic air release valves dramatically reduce those risks by maintaining near air-free flow, protecting equipment from pressure surges, and improving operational efficiency.

If your system is showing pressure spikes or suspect losses in flow, evaluate whether proper air release valves are in place — and whether those in place are sized and maintained correctly. Reach out to the team at Crane Engineering for help selecting and applying Val-Matic Clean Water or Wastewater Air Release Valves for your system today!