Where Did It GO??

joel0711 · Jul 30, 2016

Checked CYA approx. one month ago. It was as 30ppm as I wanted. Yesterday I checked again and got under 20ppm. I could fill tube to the top and still clearly see the black dot in the bottom. I'm using tfp test kit. I rechecked 4 times and still got the same results. I have added muratic acid last few weeks as PH has been going up. New vinyl liner installed at beginning of season,I do not know if this would affect PH or not. I'm trying to figure out where the CYA has gone???
I have not had to back wash as our normal rains have not happened this summer. I'm in the process of dissolving granular CYA with the sock/skimmer method to get back to 30-40- ppm. Any ideas on the CYA disappearance??

zea3 · Jul 30, 2016

It is a very subjective test to read with a +/- of 10ppm accuracy, so differences in lighting the day of the first test vs the second test could account for the difference. Had you noticed changes in how chlorine was being consumed lately?

joegus · Jul 30, 2016

As stated above, CYA testing is a bit tricky and subjective to conditions. Also, it may take 48 hours after you add stabilizer to get an accurate reading.

joel0711 · Jul 30, 2016

yes---- more chlorine use lately--

kimkats · Jul 30, 2016

I tend to lose some CYA but know mine is from rain overfill/drain. That is why I test it at least once a month just to be on the safe side.

:kim:

Isaac-1 · Jul 30, 2016

CYA does also slowly break down in the pool, although the rate is so low it is not a practical way to lower CYA when it is extremely high, this happens faster the warmer the water is, so loss of 10 ppm over the summer when the water is hot is understandable. Monthly CYA replenishment is important for hot tubs tat are constantly maintained at 103+ degrees F.

pooldv · Jul 30, 2016

CYA tends to drop 2-3 ppm per month, up to 5 ppm when it is hotter.