Filter not doing the job?

[gogolion]

Forgot to mention in my last post that I added another 1.42 gal jug of chlorine. I just did another test. FC=15.5, CC=0, Ph=7.7.

Also, as my updated sig suggests, my pool volume is actually more like 27000 gallons. So 1.42 gallons actually raises my chlorine by 3.2, not 2.5, which is what I earlier thought. Assuming that is correct, my morning bleach should have brouth me up to around 16.5 and now I'm 15.5. So I lost 1ppm of Chlorine in a matter of 3 hrs. So I'm thinking the algae isn't all dead after all, which would explain why things aren't clearing up. Does that analysis sound good? (I'm assuming my CYA measurement of 40 from Saturday doesn't need to be redone yet, besides I'm running low on that reagent, but I've got a new batch on order). I'm going to start measuring chlorine every few hours now to make sure it stays above 15ppm.

[Darkside]

i dont much about sand filters so i cant comment about backwashing, but keep it running 24/7 like you are untill the mess is cleaned up.

seems odd that you are getting a CC reading of 0 because it sounds to me like you are still fighting algae as you still found "residue" while brushing. also you lost 1PPM of chlorine in 3 hours, so something is using it. you will also need to test at night, or after the sun is off the pool, and then again in the morning within 2 hours of the sun being on the pool to see if you are losing more than 1PPM of chlorine overnight. if you are losing more than 1PPM overnight then the battle is still on!

your CYA wont change much as long as you have not added any stabilized chlorine to the pool or drained a LOT of water and refilled. if you tested 40 last week, then its probably still 40, so save you reagents for now.

this is the most important thing... test and brush often, and keep that FC above shock level AS MUCH AS POSSIBLE untill you are 100% certain all the green stuff is gone. once its all gone you will still be left with a cloudy mess. be patient and as long as your filter is working right it will get cleaned up! it took me a few days to kill off all my algae, water bugs, and tadpoles, ( actually the tadpoles were dead in minutes ) but it took a couple weeks to get clear again!

good luck!