I opened my pool this past weekend. I plugged back all the screws/nuts within the filter and pump area. I also unplugged all those in the pool and replaced those nozzles except the one in the skimmer. I only realized it when I turn on the pump/filter and it seems causes some air into the system. Now that I unplugged the one in the skimmer, I am not getting much pressure and I think there is some air sucked into the system. I tried back wash or waste or rinse, I could see there little or no pressure at all. The only nozzle seems to be OK is the one near the pump system. Any suggestion/help to fix this issue is much appreciated. Thanks!

Air gets into the pool pump mostly right at your strainer basket inches from the pump. Remove the basket lid, grease the O ring with plumbers grease or silcione gel and reinstall. Hope it helps

Air gets into the pool pump mostly right at your strainer basket inches from the pump. Remove the basket lid, grease the O ring with plumbers grease or silcione gel and reinstall. Hope it helps

Thank you very much for your help and suggestion. It helps someone like me who opened the pool the first time by myself without experience. I finally discovered what I did wrong. Even though I unplug the piece in the skimmer where the water being sucked by the pump, there was still a thin piece of round plastic cap with a small hole in the middle that I should remove but I thought that piece of plastic cap should stay there. As soon I took it out, my system pressure went back to normal. Apparently, the pump is not sucking enough water into the system because of that piece of plastic cap.