green pool

[will23]

just open pool a couple days ago. Pool is hunter green and has not improved despite aggressive shocking (using bleach).
in ground, vinyl liner, 25,000 gal, sand filter
chem today
FC 15.94 (5 gal of 8.25% bleach put in late evening for 3 days)
pH7.7
TA 59
CYA 3 (but test strip reads approx 100-i know not very accurate but don't have my own test kit)

Any suggestions?
Thanks.

[CarlD]

Guess strips are notoriously difficult to read. If your CYA is 3, FC of 16 will kill algae. If it's 100, you need FC =25.

How did you get an FC reading of 15.94???????

[Watermom]

How do you get a CYA reading of 3????????

[will23]

at local pool store...repeat was 116 more like I thought...if I keep FC at 25 that should kill algae but how low should I let FC drop? Shock weekly? If I shock that high with high CYA, FC will take a long time to drop. Pool store suggested I partially drain pool and refill.

thanks again and sorry for so many questions

[Watermom]

First off, do yourself a favor and order a kit so you can test your own pool and know that the results are something you can trust. Get a Taylor K-2006 or 2006C (better buy) from the test kit link in my signature. A pool with a CYA of 116 (and there is no way a pool store can test CYA that high and that precisely) is going to require routine high chlorine levels that other kits won't be able to measure.

Also, read the Best Guess Chlorine Chart (also in my signature) that explains the correlation between CYA and needed chlorine levels. To kill algae, you have to shock to the needed level per the chart and continue to maintain shock levels until you can do two things:

1. Go from sundown to within one hour of sunrise the next morning without losing more than 1ppm of chlorine. And,
2. Have no more than 0.5ppm of CC.

Then, we suggest keeping chlorine high for one additional day and then let it drift down but never let it get below the minimum level based on the Best Guess chart.

You can do a partial drain and refill if you want but never totally drain a pool. Some people intentionally run a high CYA/high chlorine pool for that very reason --- they can test and add chlorine less often per week.

Don't worry about too many questions. That is why we are here! ;)