If it makes you feel any better, I also have a 20x40 IG and am having trouble with mine too. It cleans the entire pool except for one corner. The weird thing is that the first two years I owned it, it worked perfectly, but now, I can't seem to get it adjusted just right. My pool guy told me to set the jet to the 2:00 position. An earlier post here said 11:00, so I am going to try that instead. I think it's just a matter of getting it adjusted correctly. I wish I would have noticed how it was set when it was working well. But that was back when I was a naive pool owner and didn't realize that there was even an adjustment.