FC went crazy!

[mikeems911]

Yesterday I tested my newly opened pool
FC 3.5
CYA 50
PH 8
Added recommended bleach, 42oz 7.5%. Tested my FC today and it was off the chart high, 21!
I tested it twice with the R0870 and once with the liquid and shaker thing, lol. Doesn't even seem possible?
BTW pool is clear. Filter is running 24/7, SWG is off for now. Till chems get settled.

 

[an1vrsy]

You’ve tested twice so I would trust your testing. But… PoolMath indicates adding 42 oz to your 8400 gallons will raise FC by 3.3 ppm. Either more was added or testing error. To raise FC to 21 from 3.5 would take 164 oz of 12.5%. It would take almost 2 gallons of 7.5 % to raise FC that high.

 

[mikeems911]

I agree, just tested twice again and it's definitely at FC 21.5.
I added cya (2lbs to go from 50 to 80) today before I retested. I'll keep my SWG off and hope the sun will eat some Cl before the CYA stabilizes it.

 

[mikeems911]

I also have new R 0870 on the way, it's only a year old but maybe it's bad?

 

[mikeems911]

Unintentional SLAM, I guess