Tonight I added some DE to my sand filter. As members have stated on this website I add 1/3c. at a time checked the pressure went up a tiny bit, waited a few minutes andded another 1/3c. waited hovered around the same psi so I added 1/3c. more went up a tiny bit more. No way near a 1lb of pressure. My gauge isn't the best but it does go down when I backwash. I'm thinking from what I read 1c. of DE should be PLENTY for the 17" 150lb sand filter. Is this correct? If I added way too much please let me know and I'll backwash ASAP.