![](https://irrigationdirect.com.au/wp-content/uploads/2016/09/Cont-air-valve-img-1.png)
When to use
A rolling seal mechanism allows small amounts of air to expel.
Once a specified amount of air builds up, the air pushes down the rolling seal, allowing it to escape
How they operate
A rolling seal mechanism allows small amounts of air to expel. Once a specified amount of air builds up, the air pushes down the rolling seal, allowing it to escape