Air Valves

air valve

Air Valves by John Valves

Air valves are designed for use in water systems and are available with either a small or large orifice. Valves can also be supplied with a combination of both a small and large orifice.

Small orifice air valves automatically release accumulated air in pipelines during normal operation. Air can enter a pipeline in several ways through pump glands, leaking joints and are sometimes contained in the fluid itself. This air accumulates at the high points of the system and may result in large pockets of air forming which seriously impedes the flow and increases pumping costs. By locating air valves at specific points in the system, ventilation of these air pockets is achieved. Thus, in turn, increasing pumping efficiencies and flow capabilities.

Large orifice air valves allow automatic ventilation of the pipeline during filling and emptying. When filling, air is exhausted at a sufficiently high capacity to prevent restriction of the filling rate due to built up back pressure. When emptying, air is
admitted to the pipeline at a rate sufficient to prevent high vacuum pressures developing

We locally manufacture and supply a range of air valves including:

  • John Fig. 761/762 Small Orifice Air Valve
  • John Fig. 771/772 Large Orifice Air Valve
  • John Fig. 782 / 784 Double Orifice Air Valve
  • John Fig. 794 Double Orifice Air Valve with Integral Isolating Valve

Frequently Asked Questions About Air Valves

Got questions? Below are some of the questions we get asked often about Air valves.

For a liquid piping system to operate efficiently, it needs to have air and wastewater gases continuously removed. Air valves exist for this purpose. They are used during operation of liquid piping systems to release air or wastewater gases that are admitted or emitted, as and when needed.

Air naturally collects at the highest points in a pipeline. This is where small orifice air release valves are usually found. When air enters the air valve, it lowers the level of the liquid inside it. Should the level drop below a certain point, the valve is triggered to open, thus venting air out of the piping system.

As the air vents from the valve, liquid re-enters the valve body, eventually to the appropriate level needed for the valve to close. This process repeats as and when necessary.

Large orifice air valves work by allowing the automatic ventilation of a pipeline during filling and emptying. When filling, air is exhausted at a sufficiently high capacity to prevent restriction of the filling rate due to built up back pressure. When emptying, air is admitted to the pipeline at a rate sufficient to prevent high vacuum pressures developing.