I have 25000 gal IG Foxx pool. I had a new liner installed mid april. At the same time I replaced the sand in the filter. Since start up I have been using the BBB method. I usually add 2 to 3 gts of 10% chlorine each day. I use Taylors FAS test kit to check FC and CC. The chlorine usually reads the same in the morning as the night before. I take the FC to 5 each night and by the next evening I am somewhere between 1.5 and 2. Over the last few days I have noticed the FC drops to 1 or less by noon. The CC has always read 0. I brush the pool at least 3 times a week. I daily brush the areas around the returns when I add chemicals.
A week ago I noticed the returns seem to have reduced pressure. I checked the pressure gauge on the filter and noticed it was a bit high. I decided to backwash and wash shocked at the color. The sight glass showed a dark greenish grey color. I backwashed till the glass was clear.
I talked to the pool store last monday and found a possible reason. When they were pumping the water out of my pool, which was almost black with slime, their pump burnt up. They finished pumping the water using my pump, supposedly on bypass. I now wonder if I have an algae prob.
The water is crystal clear. I see no signs of algae. There is a bit of sand on the floor but that is from the grandkids using the pool. I am able to vacuum it easily. I does not disperse like algae always does when I brush it.
I brought the FC up to 5 at 11:00 last night. I checked it again at 1:00 this morning. Still at 5. At 8:00 the FC was at 3 and CC at 0.
Here are my latest test results.
Is it time to shock? According to the pool calculator I need to take the FC to 11 and keep it there. Do I need to add an algecide. Without seeing any algae, I'm not sure which one to get.
I also have a hard time keeping the PH below 7.8 or 8.0. I have added acid 3 times in the last month. The PH drops to 7.4 and gradually rises to the current level over 3 to 4 days. I have my jets pointed up to improve circulation. The water is swirling at a pretty good rate but there are no bubbles.
Sorry for all the questions but could sure use some advice.