I noticed yesterday that there are small bubbles coming out of the return closest to my pump. Upon closer inspection the skimmer closest to the pump (which is next to the previously mentioned return) isn't full of water. Instead, water is rushing in to the skimmer. I went to the pump and the strainer basket is about 25% full of air. I double checked that the o-ring isn't worn, it's not, and applied lube to help the lid seal. I then checked the drain plug and all was fine there too. Here is what the skimmer looks like. The water is coming from the left side of the picture.
When I turn the valve for that skimmer off I don't have any issues. I'm thinking there is a leak on this line. What are your thoughts?