Although there are plenty of informative posts about unexpected CYA levels upon opening, I post mine because of unexpected results based upon the quantity and types of chemicals added over the past month.
The pool was closed early September 2015.
- Balanced with a CYA value of 60
- Water lowered under skimmer
- Protected with a solid cover
One week before Memorial Day 2016, with city water added to mid-skimmer, I was surprised with an initial CYA value of zero. I admit to being uncertain if I tested before or after starting the pump. Although my reagent was within date, I was perplexed enough to seek a second opinion. I am absolutely certain that the pump was running for several days before I pulled a sample for testing by my local, independent pool store. Their test, just before Memorial Day, also showed CYA to be zero.
Since then, the following actions have been taken.
- Over the first three weeks, regular additions of liquid and granular kept the pool sparkling with a consistent chlorine level of 3-5.
- During this time, I utilized 10 gallons of liquid 12% and 15 lbs. of Dichlor-S-Trianzinetrione.
- While my expectation was that CYA was slowly increasing, it appeared to barely budge based upon my kit, and supported the apparent chlorine demand.
- Last week, the cloudy green hue of trouble appeared.
- Out of liquid and unable to resupply due to ankle surgery, I added 4 lbs. of dry stabilizer via skimmer sock and broadcasted my final 10 lbs. of granular Dichlor.
- Today, CYA is suddenly reading 80 at the pool store and over 100 by dilution test with my kit using new reagent.
- Chlorine is near 15 by my distilled water dilution test.
- Green is the color of the day, although with reduced cloudiness.
Based upon the calculator,
- 4lbs of dry stabilizer (64 dry ounces) should result in a CYA increase of 15 for my 33k gallons.
- Adding 25 lbs. of Dichlor (400 dry ounces) should have resulted in a CYA increase of 46 for 33k gallons.
- Total CYA should have increased to 61, assuming zero start, (higher than desired but I panicked)
- Yet it reads at least 80 by one test and over 100 by another.
I’m beginning to suspect that the opening CYA value of zero was incorrect and that a healthy amount was hiding with the intention of messing with my sanity.
Thoughts and questions from the group are greatly appreciated. Thank you.
CYA unreliable results to date