For the first time in 8 years, my pool PH is varying wildly. Usually in Texas in August, the PH gradually goes up and I add acid about once a week. Now, the PH will read 7.7 one day and 6.9 the next day. I retake it in a different part of the pool, and it reads 7.9.
I have to take it several times and finally decide based on several different reading whether to add acid or not.
I have two testing kits and they both seem to read the same.
Is there a reason that the PH could go down to 6.9 overnight?
Our pool is 20,000 gallons, temp. 86, Chlorine 6 (I use bleach), Total Alk 60, Calcium 300, CYA 50, plaster pool.