My pool is a real mess. I this is my 3rd summer with this pool and Im having problems I don't recall from the previous years. From reading, I probably need to slam it, but I thought I should vacuum it to get the visable stuff off the bottom first. I am using a manual vacuum on my above-ground pool. when I turn on the pump to start the vacuum with the filter in the filter position, there is air coming into the pool through the return. i thought this was normal as the vacuum is working. After about 15 minutes, it seems like stuff is coming back into the pool through the return while I'm vacuuming. I have back washed and rinsed the filter twice But it continues to happen. Is it normal to have air coming through the system when I'm vacuuming? I is not happening when just running the filter, its pressure is always at around 15 psi. I have filled the pool as high as possible. any insight would be appreciated.