CYA Test Results - HELP

keyser777 · Sep 1, 2012

I bought a TF100 test kit a few months ago. Prior to that I had been using the "guess strips" from local pool stores. When I got the TF100 I also ditched the 3" chlorine pucks I had been using since I got my pool 3 years ago and switched to BBB. When I measured my CYA levels with the TF100 kit they were at or slightly above 100 so I did an about 75% pool drain and refilled. I got all my numbers back in line - pH, FC, TA, etc.

Even after the draining and refilling my pool the CYA levels were measuring around 90-100. At least that is the number that I kept getting. I know this test is subjective so perhaps I'm not reading it right. Here comes the rub, my pH levels have been at 7.5 for at least a month without having to add any Borax or acid to adjust. The day time temperatures have been around low to mid 80's and night time temps in the upper 60's to low 70's. We haven't been swimming in the pool too terribly much due to busy schedules this past month. That being said, I feel like I'm burning up a lot more bleach then I should be for CYA levels that hover around 100.

Is it possible that I'm just not reading this test correctly? I watched a You Tube video of someone doing this test and I feel like I'm doing it exactly the same way. However, my FC are dropping 1 - 2 ppm per day. From what I understand, that drop is typical of pool water with much lower levels of CYA. When I test the CYA using some left over "guess strips" the readings are in the 60 - 80 range depending on which kit I use.

Am I missing something here or am I just not able to perform the CYA test accuratly? I have an eye exam next month, so maybe my eyes are deceiving or I need a new prescription.

Richard320 · Sep 1, 2012

1-2 ppm per day sounds reasonable. Super-high CYA doesn't decrease the usage that much if you keep FC where you should, so that you have enough 'unbound' chlorine to fight algae. All the super high CYA level means is that you have to maintain a much higher minimum FC. Let's say you're at 80, sort of the midpoint of all the tests. FC should never dip below 6, which is going to be unreadable using a color block test.

spidey07 · Sep 1, 2012

The test maxes out around 100 so it's possible your cya was much higher than 100 to start. Which is very possible with trichlor for 3 years. I'd trust your testing.

blondemarcello · Sep 1, 2012

Someone told me that if you doubt your CYA reading because it is so high to dilute it. 1/2 pool water, 1/2 tap water and then run the test. Results would be times 2 for CYA reading. It helped me clarify that I was at 90.

cody21 · Sep 1, 2012

to the experts: Is what he said true ??? 1/2 & 1/2 ??

Richard320 · Sep 1, 2012

cody21 said:
to the experts: Is what he said true ??? 1/2 & 1/2 ??

Yes. But you lose a little accuracy. So if you decide it's reading between 50 and 60 with the diluted sample, you can really only say you're between 100 and 120.

Leebo · Sep 1, 2012

It sounds like you're testing right. A lose of 2FC is normal....even at 90CYA. I'd keep running the pool the way you are, and look next year to lower the cya more.

Edit.....that is assuming you close the pool for the winter.

keyser777 · Sep 1, 2012

Leebo said:
It sounds like you're testing right. A lose of 2FC is normal....even at 90CYA. I'd keep running the pool the way you are, and look next year to lower the cya more.

Edit.....that is assuming you close the pool for the winter.

Yes - I live in the northeast so pool closing right around the corner.

Thanks for everyone's help and opinions!