Sucking noise at the skimmer/jet area

[Brookesmith]

Hi there, there is a sucking noise at the skimmer/ jet area? What could be causing that?

 

[zea3]

Hi, welcome to TFP! How high is the water level in the skimmer? It should be at least 1/2 way up the skimmer opening. Also check if the weir door in the skimmer opening is stuck down. It should be free floating in the skimmer opening.

 

[Richard320]

My first guess would be low water level. Second would be a sticking weir causing a low water level in just the skimmer.