Hello everyone. I am new to the forum. I have a 150lb Hayward sand filter. My problem is that when i swept the pool all the algae that was on the bottom didnt filter out. It just blew back into the pool thru the return jet. Also when I back flush the filter the water goes thru the waste hose and the return jet which puts the nasty stuff right back into the pool. Any ideas on what my problem could be. Filter is about 4 years old.