Airline in Durso Breather Hole Purpose

[SteveMM62Reef]

What is the Reason for putting a section of Airline in the Durso Vent/Breather, going down into the Down Pipe ?

 

[KrisReef]

To conduct air down into the area where a siphon might form, ie to function as a vent pipe?

 

[Sod Buster]

Yes. It helps with the gulping sound the drain makes. Leave it long and fine tune it moving the airline up or down for the least amount of noise. When it is as quiet as you can get it, trim the extra off the top.

 

[malacoda]

+1 It reduces the gurgling noise by allowing air to escape the pipe without getting 'entangle' in the water. As Sod Buster said, by moving the air hose up and down within the pipe you can tune it until you find the position that reduces the gurgling the most.