My son is helping a neighbor with his 17,500gal. plaster SWG pool. We have been using the TF method on our pool for 2yrs. now with SUCCESS!! We used our Taylor TF-100 and got all of his values to start w/owner supplying additional phosphate value from pool store. They are dying to sell him Phosphate Free chemicals. His FC was 0 which we expected since there was algae in the pool. We inputted all of the values into Pool Calculator and have been shocking EVERY day e.g. attempting to get FC to 15ppm for almost a week now and the highest reading we have gotten is FC 2ppm with adding 6% bleach per the pool calculator every day!!!! There is still algae in the pool too. Why are we not able to get any higher reading for the FC? Son has only been testing each morning. Do we need to add more bleach than the Pool Calc. suggests? I know that the algae is consuming the chlorine, but I would think that we would have reached higher FC readings? He has been running the filter pump 24/7 and he just had all of his equipment checked. We have not gone back and re-tested other values thinking that we needed to first get the FC up and get rid of the algae and then get everything else balanced.
What are we doing wrong? HELP!!!!

TIA!

SWG
17,500 gal.
plaster
FC 0
TC 0
Salt 2900
CYA 100
TA 190
pH 8.0
phosphates 100

You should read the article on how to shock your pool in Pool School. You need to add chlorine at leat twice a day, preferably more often the first day or two, or you won't make any progress.

You have another problem as well. With CYA that high you are going to have a very difficult time. I recommend replacing water to get CYA down to around 50 or 60 before trying to fight the algae. While you are working on that, do some additional reading at Pool School, and soon enough everything will be back on track

Gotcha!! Just went back to Pool School and yes, now I see the error of our ways. We need to hit it HARD right off the bat and yes, will have to be twice/day in order to get ahead of the algae growing back. I will first get the pool owner to remove water and add some 'fresh' first. This gentleman is as nice as he can be, but is having a difficult time understanding and following through.

Thank YOU!!

I have similar issues, but have not been adding chlorine this often. I am gonna increase it now.

Thanks