in groung pool
mrmarmot asked:

I have a 22,000 gallon in ground fiberglass pool. I havent had this problem in prior years. The latest readings (after several rounds of shock including 10 bags 4 days ago) are as follows:

CYA – 150
Total Chlorine .6
Free Chlorine 0
Ph – 7.2
Adj Total Alkalinity 179
Total hardness – 278
No algae

Even after adding 10 bags of high chlorine (over 60%) shock the reading was only 6 for chlorine and it dropped to 1.0 the next day. Usually it would remain high for days in years past.

I dont have chlorine lock and I’ve done the OTO test so its not a reagent bonding issue. I also took a cup of the water and added some chlorine to it and then it does test high so not being blocked. I did the dilution test and know that its not an issue of over chlorination.

The only new thing this year is xialite replacing the sand in the filter.Any suggestions before we try draining the pool? We’ve gone through more chlorine and shock in one month than we even come close to in a seaso