Durso question

[fe342185]

I put a durso inside of my HOB overflow and all seems well but ever few minutes there would be a gush of water and it gargles. What do I need to do? I have experemented with different size vent holes and still no luck. thanks

 

[Entropy]

http://www.dursostandpipes.com/


"If you drill a hole and the water level still drops to far (making a sucking noise) then the hole is to small."