I'm not even sure if this is the correct model, as the company is no longer in business and the literature is sparse. The skimmer has two adjustments - a telescoping riser pipe on the outlet of the main chamber and a needle valve for the air intake. I can't find instructions anywhere. A few questions: 1) What water level should the skimmer be sitting at in my sump? 2) I assume the telescoping riser helps to adjust the water level inside the main chamber? Is that true? If that's the case, what is the target water level? 3) It would seem most people leave the needle valve fully open. What would be the condition under which you would throttle the air intake to the impeller? Here's a photo of the skimmer in question.