My above ground pool is consistently dirty even after I vacuum. By the time I am done with one end the other end is dirty. The main problem is a very fine dust that dissipates when you touch it, but it is also larger debris. At the start of the season I replaced the sand in the filter and the multiport valve is only a few years old. I have tried backwashing but it comes out clean. I can see some debris blowing out of the input valve that delivers the clean water. I have also noticed that in the skimmer it is creating little whirlpools that is sucking in air and making a gurgling sound. It is the same pump that I have used for years.