Air Release Valves

Air is the enemy of any pressurised pipeline. When a water main is filled, air is displaced towards high points where it accumulates in pockets. Under operating pressure these pockets compress and restrict flow, raise energy consumption and accelerate corrosion of the pipe wall. In severe cases, rapid air release creates pressure surges capable of causing valve slam, pipe joint failure or structural damage to adjacent infrastructure. Correctly specified air release valves eliminate these risks at source.

A combination air release valve performs three functions in a single body: it vents large volumes of air through a large orifice during pipe filling, releases small air pockets through a small orifice under working pressure and admits air during drain-down to break the vacuum and prevent column separation. This three-in-one function makes the combination valve the standard choice for most water main installations and the default specification on European water utility frameworks.

For pump stations and transmission mains where pressure surges are a known risk, anti-shock air release valves add a hydraulic throttle on the air inlet stroke. This controlled admission of air prevents the pressure spike that occurs when a collapsing vacuum suddenly admits atmospheric air. The KAR5, with its adjustable throttle, is widely specified by water utilities and EPC contractors for pump stations, pressure zones and rising mains where water hammer risk is elevated.

Sewage and wastewater pipelines require specialist air valves. Sewage combination air release valves are designed with floats and seals resistant to fouling from solids, grease and biofilm. The SKAA anti-shock sewage air release valve and the SKAR and SKAS ranges are suitable for gravity sewers, sewage rising mains and industrial effluent pipelines where standard clean-water air valves would rapidly fail due to fouling of the float mechanism.

Air release valves should be installed at all high points on a pipeline, immediately downstream of pump stations, at changes in gradient and at intervals along long horizontal runs. Correct sizing requires knowledge of the pipe diameter, system pressure, filling rate and topographic profile. An over-specified valve opens unnecessarily under operating pressure and may admit insects or debris; an under-specified valve fails to clear air quickly enough during filling. AFC Valves Europe can assist with sizing calculations and valve schedule review for new mains and rehabilitation projects.

All air release valves in our range are manufactured to ISO 9001 and are available with WRAS approval for drinking water duty. Full documentation including test certificates and material certificates is supplied as standard with every order.