I think my overflow is getting air trapped in it or something because the flow of it keeps slowing down then the water level in the tank will rise to about 1/2" below the top of the tank the it will start siphoning really qiuckly until it gets back to the top of the intake, it's kinda scary.
this is my overflow.
but after I took this pic I realised the intake was to low so I added a 45 elbow to the end of the 90 elbow so the water line would sit a little higher.
45 degree elbow
Do you think this could be sucking in air?
I think I might have to take the overflow out and cut of the elbow from the intake and add some kind of straight extender PVC fitting, so the intake is just a straight pipe with no elbows. Would that make a difference?
EDIT:Wow you gotta check this out, clear PVC!!!
http://www.clearpvcpipe.com/index.asp?PageAction=VIEWCATS&Category=37