Chlorine block

[Racing Rob]

Hello all,
Need your help and suggestions.
27’ round above ground pool.
I opened the pool 2 weeks ago. Water was clear. Water level was about 7” below the skimmer. I filled the pool and added 2 gallons of liquid chlorine and let the pump run about 24 hours. Took a water sample to the pool store and he says I have a chlorine block. I’ve never had this before. He says I need to add about 18 gallons of liquid shock and run pump for another 24 hours and retest.
My free chlorine is .45 (low)
Total chlorine is 1.59
PH 7.9
Total alkalinity 176
Calcium hardness 176
Cyanuric acid 5

Not sure if I need the 18 gallons or what to do.
Please help
Thanks
Rob

 

[Mdragger88]

I think u mean “chlorine lock” but regardless- this pool store term is a Fallacy & ignores the fc/cya relationship.
FC/CYA Levels
Your fc has gotten too low & this has allowed algae to grow.
To remedy this you need to do the SLAM Process.
In order to perform the slam & properly care for your pool you must have your own reliable, accurate test kit. K2006c (found online) or TF100/pro available @ www.tftestkits.net
We can’t really give much more advice based on pool store testing as it is fraught with inaccuracies.
You will need the liquid chlorine BUT not all at once!
If your cya is even close to accurate the pool store has u on the fast track to bleach your liner in short order or at the very least shorten it’s life drastically.

Until your kit arrives, just add 5ppm worth of liquid chlorine to the pool daily to prevent it from getting worse until u can tackle it properly with accurate data.
Use PoolMath to calculate amounts.
When u get your kit, post the results here & we can help u along.

 

[Racing Rob]

Thanks so much. As of now the water is clear and have no visible signs of algae.

 

[Mdragger88]

In that case - to be sure you need to do an Overnight Chlorine Loss Test.
To do this & follow the other tfpc protocols an appropriate test kit is needed.
Pool Care Basics