I got a new bottle of Taylor R-0013 reagent yesterday and noticed the CYA test result came in 10 ppm lower than with the last bit of the reagent left over from last season.
I have read several threads on the Taylor CYA test on this site and am aware of the subjectivity (and hence uncertainty and inaccuracy) involved with this test, but here I did a test with (what I believe to be) fresh reagent and compared it immediately afterwards with the results conducted with reagent I had been using and got distinctly different results.
So, the new reagent gave me a lower reading (20 ppm) than the older reagent (30 ppm). Actually, the 20 ppm was even lower, because the black dot was still slightly visible at the 20-ppm mark.
The new reagent has an expiration date of 8/2017 and was bought from PST Pool Supplies in California a few days ago. The older reagent I bought in July of last year from TFTestkits. I'm using a TF-100 test kit.
I'm currently in the process of raising my CYA level and am targeting 50 ppm. My problem is that the skimmer in which the sock with CYA granules is placed has almost no suction, so the four pounds of CYA I have placed (not all at once) in the sock over the past couple of weeks have now only gotten down to about 2 lbs. I think I will place the sock near a return very soon, because it's taking so long to dissolve.
Also, I believe my pool has a leak, but I'm not certain exactly how much it loses. I'm guesstimating a figure somewhere in the 1,000 gal area per week. So, CYA is somewhat of a consumable for me at this point. I'm currently only adding CYA and liquid chlorine to my pool. The other parameters stay in check without me doing anything about them, probably due to utility water being added regularly and in large amounts.
I've been a pool (and house) owner for a little over a year now with no prior pool care experience. The pool came with an autofill device that the previous owner must have installed.
Here is a link to a Google Spreadsheet with my recent pool test results:
Note, that if you're looking at the two charts in that spreadsheet that on the more complex one the scale on the left y-axis is to be multiplied by 10 for CYA and water temperature (in °C). So, a reading of 2 for CYA is actually 20. Also, test results are graphed as lines, chemicals added are graphed as columns. CYA added is in lbs, liquid chlorine (10.5%) in gallons.
The fluctuations in FC displayed are due to me testing immediately before and three hours after adding chlorine.
In case you can't open the above link to my pool test results, the most recent test results yesterday were:
- FC 3.0 ppm
- CC 0.25 ppm
- CH 200 ppm
- pH 7.7
- TA 110 ppm
- CYA 20 ppm
I am adding 0.5 gal of 10.5% liquid chlorine every evening. Have added about two lbs stabilizer five days ago.
It is a little disconcerting to me that the CYA test is so unreliable - besides the subjectivity. Two different lots from the same manufacturer give such different results? Can anyone explain this? Is one of my reagents compromised? If so, which one? Or is it normal that the reagent skews the results over time?