I have a sand 500 lbs sand filter and have noticed dirt on my steps and cozy cove. I will brush my pool including the steps and cozy cove and the next day dirt will right back on them. There are reruns at both locations. Is this just a disadvantage the sand filter has being it can't catch the dirt or do I need to open it up to inspect the sand. Sand is only 9 months old. I have also experimented with de and that seems to help some.