Here are pictures of my pentair sand filter with t push pull valve and pipes. When I did my chemical test on my pool, my CYA level is about 100 so I wanted to drain and refill slightly to help balance that out. Either through backwash draining or vacuuming to waste, the latter is preffered as my pool is pretty green and I'd like to vacuum out some algea. I dont really understand how it works with my plumbing though. I closed my bottom drain valve, set the plunger down to backwash, and hooked my vacuum to the skimmer. No suction. Then when I set the filter to filter mode, I get the normal amount of suction. Another issue I have is we dont have sewers and I when I backwash normally, the water doesnt drop really at all even when I run it in intervals of 5 minutes. I cant find where the previous owner plumbed the backwash water to go but I think it's a dry well somewhere on the property. I'm going to try some bioactive to see if I can reduce the CYA levels that way, but I'd like to figure out these backwash issues for the future. Any tips on the above would be very much appreciated as I'm pretty stumped. Thanks in advance!