You guys have all been super helpful with loads of other questions I've had, so I hope someone can help me here, too.
I recently completed a SLAM (Algae or pollen? (Lots of pictures)) see there for the progress). I added DE to my sand filter following the instructions from pool school. My beginning preassure was 14.5 and I added DE until I got to 15.5, which turned out to be 1.5 cups. I started noticing some strange behavior where my filter would seem to spit out a cloud of dark junk when the pump would start. Given that and seeing more brown junk on the bottom of my pool a few days later I was suspecting more algae, so I vacuumed the bottom, backwashed just in case (my preassure wasn't up high enough but tons of really dark water would come out), and slammed. However, I passed the OCLT (How O need the OCLT be?) the first night, had <0.5 CC, and my water was clear againthe next morning .
After that I back washed and deep cleaned my filter because I thought the cloud spitting was the result of a channel or something in the send, following the instructions stickied to this section of the forum. I didn't see any channals, the sand level looked fine (I guess), and not much large particles, but when I stuck the hose deep in the filter lots of really fine looking greenish brown debris came up through the center pipe. It looked like the mixed up DE in the bucket, but much darker, or like the fine junk that collects in the bottom of my pool Finally, I put everything back together and added some DE to my sand filter until I got to 15.5 psi again. On the first run the preassure ran up to 18 or so, but I didn't want to backwash too early since I often see warnings not to backwash before pressure gets to 25% up. I had to clean out my skimmer basket though, so I turned of the pump, dumped the leaves and sticks (we had had a storm), and as soon as I turned the pump back on a plume of yellow brown muck shot out the return jet and the pressure fell back to 14.5. There was also some brown stuff on the bottom of my pool, but I had to tend to some renovation projects and didn't have time to vacuum. Of course right then the diaphragm of my auto cleaner had to break, so I just let the filter run. Yesterday I checked the water and it was pretty cloudy (I hadn't added FC since I passed the OCLT during the SLAM. My FC then was 17 at CYA <40
I found 4.5 FC, 0 CC, PH 7.6.
Today the water was even more cloudy, and I finally got to vacuum. I got smart to what was happening, so after I vacuumed I turned the filter off, set it to "rinse" and sure enough I got a stream of brown gunk out of my waste hose.
Here is what I think is happening: The DE ends up clogging up in front of the laterals when under pressure. When the pump stops things settle, but when I turn it back on the DE and all the junk it caught goes through the lateral (because it's a sand, not a DE filter), and comes out the return.
Today's numbers from after that were FC 3 and PH 7.6, so I added 2 FC worth of chlorige. Still not enough loss on a sunny day to suspect algae, and again, this is after a SLAM that passed OCLT without FC ever dropping below the minimum. The water also was clear, so all that came in was pollen, dead leaves (a tree trunk above my pool died in the spring so I got fall all summer yay!), and the DE
So, now I guess I have about 1 cup of DE floating in a pool with a sand filter incapable of picking it up. But, something else might be going on. Is there a different explanation for the dirty water coming in the pool when re-starting the pump? Or why else is my filter just catching junk only to release it again on the next pump start.
My questions are: Is this a case of DE in sand filter straight out failing, and has anyone had that happen before?
How to fix it? (My best guess is throw in more of the clarifier that I still have sitting around from the previous owner, vacuum it up, backwash, and then clean the filter again.)
Any other ideas for getting DE out of a sand filter pool, if that is the problem?
------ Please disregard anything below. My 3 year old daughter just came home from a long stay with grandma and really wanted to take turns writing and I couldn't say no. --------
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