When should you backwash a DE Filter? I have seen on this forum 2 different references of when to backwash a DE Filter.

1. When PSI rises by 8, or
2. When PSI is 8-10 over the "clean" setting on the PSI gauge.

Which is correct?

I am operating under the guidance of #2 above. Currently my PSI gauge is around 18psi. According to my gauge, I would be due to backwash around 28-30psi.

Here is a link to what my PSI gauge looks like (http://i22.ebayimg.com/02/i/000/a2/9c/fda2_1_sbl.JPG).