I have an 18'x36' inground kidney shaped pool (22,500 gallons). Towards the end of last summer the water looked good but I had no chlorine reading. I assumed my 7 year old swg system met the end of its life. I now just opened the pool and fully replaced the swg system. The water looks perfect but I still can't get a chlorine reading regardless of whether I run the swg at 100% or if I dump 2 pounds of shock in. Water test results: chlorine 0, ph 7.2, alkalinity 50, calcium hardness 140, cya 75, phosphates 100ppm, nitrates 30ppm.
I didnt bother adjusting the alkalinity or calcium hardness yet because the pool store told me to drain and refill due to nitrates. Since learning that nitrates usually come from fertilizer, I noticed that my lawn company uses a rotary spreader that shoots out the fertilizer. In fact there is usually fertilizer on the pool deck after they come. I imagine that's how I got the nitrates. Needless to say I will discontinue with the lawn company.
My pool install company said to drain half the pool and refill? Any thoughts?