Potable Water Supply Recommendations

Air Valve Recommendations
Free and dissolved air exists in all fluid transmission systems.
The principal sources for this air are:

• Incomplete filling of the line – which leaves air pockets in high places and in different accessories.
• Air dissolved in the fluid that is released when the pressure drops and/or there is a rise in temperature.
• Vortexes in the fluid, at the points from where it is pumped, introduce air into the system.
• Air is sucked into the system through openings and accessories.

The lack of control over the air present in a fluid system can result in damage:

• If destructive vacuum conditions are created.
• The presence of air can have a detrimental effect on system drainage efficiency.
• Air pockets in the system cause reduced sectional cross flow, higher energy losses, tremors in the system and in extreme conditions; the entire stoppage of flow.
• High pressure surge.
• Metal parts in the system and system accessories corrode at higher rates.
• Lower pumping efficiency.
• Physical risk – when large volumes of air under pressure are released at high velocities.
• Inaccuracies in the measurement of fluid volumes.
• Accelerated wear of moving parts and flow gauges.
• Cavitation damage.

Control of Air in Potable Water Systems Using A.R.I. Air Valves
There are three main types of air valves installed in potable water supply systems: air & vacuum, automatic air release and combination (double) valves.

Air & Vacuum valves discharge large quantities of air from non-pressurized pipes and are used mainly when filling a line. Air & vacuum valves also make it possible to admit large quantities of air when lines are drained and when the pressure drops suddenly. Air & vacuum valves are also known as: kinetic valves; large orifice air valves, vacuum breakers, low-pressure air valves and air-relief valves.

Automatic air release valves continuously release relatively small quantities of air from a pressurized line. The automatic air release valve is also known as a small orifice air valve and as a pressure air valve.

Combination air valves fulfill the tasks required of both types of valve – air & vacuum and automatic. In other words – they discharge or intake large volumes of air when filling or emptying a system and continuously release small volumes air when the line is pressurized.

Combination air valves are also known as double orifice air valves.