Loud Overflow Box Suction Noise

I have an overflow box emptying into my sump, and for some reason it makes a loud and very annoying sucking noise from time to time out of the PVC intake part in the back of the overflow box. Somtimes I can stick my finger in there and stop the noise, but than it starts back up again. Does anyone have any ideas how to stop this from happining? My system is very quiet, and this is annoying the hell out of me. Thanks!

 

you can try pushing a piece of 1/4" flex tube into the opening to adjust the noise (like you do with your finger)
another way is to increase the flow from your sump

 

how can i increase the flow?

 

bigger return pump, simple.

I place a small towel over the top of my overflow box and it seems to muffle the noise.

 

i wonder if i lowered the intake part of the overflow box in the aquarium if that will raise the amount of water

 

no that just effects the height of your DT water level

 

guess i will try to stick something in the opening to break the suction i just bought my return and im not getting another one