I manage a 99,000 gallon plaster in-ground pool with sand filters and I can't recall the flow rate or pump size... both of which have been used on this pool for years. The most recent levels are Cl: 1.0. Ph: 7.6. CYA: 0. TA: 90. Clarity is very clear. Temp is around 83 depending on the time of day. My supervisor, who taught my CPO class, came out with a repairman but couldn't find anything amiss. Several hours ago I added 30 scoops of cyanuric acid as suggested by my supervisor.
I've run the chlorine pump for eight hours several days and cannot get the level up. It peaked at 5 several times but never lasts. The Ph stayed at 8 for several days. I got it down to 7.4 two days ago and tried shocking the pool with several chlorine sticks but again it doesn't last.
What could be killing the chlorine? I've gone through almost half a tank in one week. The pump is working fine. This is my first summer as a CPO. This is the first year with this problem but last year's staff is as stumped as I am.