We have a quad DE filter. The directions say to backwash filter when the psi gets to 10 above the start up number (hope that makes sense). Ours never does. It only moves 2-3 psi above. How often do most people backwash. I know this would depend on pool maintance but I have no clue when we should be doing this. Also, you know the "eye" things on the equiplment? What is that there for? Is it suppose to tell you something? Lord, I sound like a complete idiot. We just backwashed 2 eeks ago b/c our pool was hit with serious construction waste from a patio we put in. That eye ball is green now although my water looks okay and my numbers are all with in range. I have been seeing this yellow stuff on the walls of the pool which I thought might be pollen but I will post in the algea section. TIA!