Eight year old 22,500 gallon pebble finish gunite pool in Massachusetts with DE filter and heat pump. On 6/12/2016 the stabilizer level was 51 ppm. On 8/15/2016 it was 70 ppm. And on 8/29/2016 it measured 84 ppm. The first and last tests were performed by the same pool place; the middle result was done by a different pool place. During that time, I added just six 3-inch trichlor pucks when I was away for 8 days. The rest of the chlorine came from 8% sodium hypochlorite bleach.
So how can my cyanuric acid level rise so much when I've hardly added any stabilizer? I would expect the CYA level to rise maybe 7 or 8 ppm based on the CYA content of the pucks. I have stayed away from trichlor because I wanted to keep the cyanuric acid level relatively low. The only other chemicals I add are muriatic acid and sodium bicarbonate. Can these test results be accurate? What is going on here?
Please ignore the pool information immediately below--it somehow gets attached to my posts.