alkalinity

[terrak]

i have a 30,000 gallon inground pool- approximately 6 years old. i havent had any real main concerns until recently.
at the end of 2012, my cya was over 100, so i quit using sticks and chlorinated with bleach only. well this year, upon opening, i'm told (by pool store) that my cya is still over 100 (my taylor test reads 70) and that i need to drain my pool. i guess i'm confused as to how it's still that high, even though i havent used any stabilized chlorine and drained almost half the pool before closing in 2012?
do i really need to drain the pool? also, the pool store is saying my TA is low (due to cya)......
my readings:
FC: 3.5
CC: 0
PH: 7.4
TA: 110
CH: 210
CYA: 70
borates: 50

pool store readings:
FC: 3.5
CC: 0
PH: 7.4
TA: 102
ATA: 69
CH: 218
CYA: 100

 

[JohnT]

Welcome to TFP!

Trust your own readings. The CYA test isn't accurate at extreme levels, so a reading of 100ppm could actually be 200ppm or more.

Your TA is fine.

Your only real issue is that you should maintain a higher chlorine level with your CYA at 70ppm. You should follow the Chlorine CYA Chart

 

[terrak]

thank you for your response!!
so what you're saying is: i dont need to factor in the high cya reading when testing for alkalinity? and i dont need to drain my pool? the pool store wants me to add 10 lbs of alkalinity increaser and is making me feel like my own cya reading is wrong. (i purchased the "dummy" solution and practiced doing the test, so i'm fairly confident in my findings).
also, how high should i maintain my FC levels until the cya is at a more appropriate level?

 

[terrak]

sorry- i just saw the chlorine cya chart you posted....duh!

thank you for your help!

 

[JasonLion]

Don't do the CYA correction to TA. Around here we always use the TA number directly from the test kit. The adjusted TA value only matters if you need it to use the outdated way of calculating your saturation index, and there isn't even any reason you would need to know the saturation index.

 

[terrak]

awesome!!! i appreciate your advice!!!!