Installation of air valve on a wastewater discharge network?
asked 24 February 2016 asked by soma2012 (330 points)
Hi, No, you don't have to, because an air vent (valve or other) is designed to work on a pressurized network, but the point in question will not be constantly pressurized. The air will escape 'naturally' through the manhole at the connection between the discharge pipe and the "gravity" pipe! However, be careful about where you put the manhole, because it might cause odour problems...
Hi, On a discharge network, it is crucial to install an air vent if there is an active high point anywhere on the system. Check the hydraulic design of the pipe network. Once installed, this high point should be monitored and routinely maintained. Otherwise (if this high point is not equipped with an air vent or if the existing one is not properly maintained), air will accumulate at the high point and restrict the flow of water. In an extreme case, this obstruction could entail having to invest in auxiliary pipes, a totally unnecessary expense. So watch for that! Kind regards,
Hi, I agree with you about the importance of an air valve at the high point of a pressurized pipe, but in the scenario described above, the discharge is in a "swan neck" section with the outlet immediately after the high point, so an air vent is not necessary. Kind regards,
Hello, I can confirm that an air vent is not required in the case described here, unless the gravity portion of the network is particularly long and that head loss causes pressure to the right of the high point. In which case you would find yourself with a pressurized pipe where an air pocket could form. With nominal flow, head loss in the gravity section should be less than the difference in height between the high point and the discharge.