Increase in CYA ?

[DPR]

Several weeks ago I did a series of drain and refill to lower my CYA. On July 26, CYA measured 50 and I stopped draining and refilling. Since then I have only added liquid chlorine and muriatic acid to maintain the PH.
Results from a full test today:
CYA was 90 - 100.
PH =8.2
CL= 1-2.
FC=2
CC=0
TC=2
TA = 77
CH = 275
I know I need to add muriatic acid and chlorine (been out of town for a few days) but what would cause the CYA to rise?

thanks

 

[Donldson]

CYA does not increase unless you add it. How did you get a TA reading of 77?

 

[Sunnydaze]

It didn't increase if none was added. At least one of the tests were incorrect. Try another CYA test and see what you get.

If you took the 1st cya test while you were still refilling, maybe the pool water wasn't thoroughly mixed and you got some fresh water in the pool sample.

 

[DPR]

Wow so nice to get such quick responses - thank you.
Donldson, you are correct - thanks for the catch. My TA is 70 not 77 - ( mistakenly multiped by 11 -misread the testing instructions).
Retested this am and CYA was 70.
After adding both Muriatic Acid and Chlorine last night. PH 7.5 CL 5
CYA still somehow increased from 50 a few week ago. Is it possible that the liquid chlorine I added had CYA?
Is it common for the CYA test results to vary? (using the TF 100 test kit)

thanks everyone.

 

[HermanTX]

CYA still somehow increased from 50 a few week ago. Is it possible that the liquid chlorine I added had CYA?
Is it common for the CYA test results to vary? (using the TF 100 test kit)

One - the stabilizer takes 48-72 hrs as minimum to mix and settle so possibly your initial test after fill was not thoroughly mixed.
Second - the only chlorine with stabilizer in it are trichlor pucks and dichlor 'shock' - and they only add when they become fully dissolved which could be several days depending on how long your pump runs.
Third - the CYA test is one of the most subjective tests - I do it by pouring the solution to a known level such as 90 then peer in and see the dot, then I pour solution to 80 and peer in, I do this repeatedly until I do not see the dot and then select the value where I last saw the dot. This helps me because I am not consistently looking down at the dot in the tube while pouring the solution. I have more consistent results. Also, best to have sun at your back so you are looking down the tube in the shade of your body.

 

[DPR]

good advice on how to administer the CYA test. Thanks

 

[ddoggphx]

The CYA test is so frustrating. I wish there was a better way.