CYA Testing and Adjusting

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bluenoise

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LifeTime Supporter
Jul 25, 2007
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Alamo, CA
A few weeks ago, I tried testing my CYA but found I didn't have enough reagents to do the test. No problem. I ordered a refill and took a sample of water to the pool store in the meantime. I suspected my CYA was low since I had replaced so much of my water since last Summer and I was having trouble keeping my FC up. Sure enough, the pool store's test tells me my CYA was about 30. I bought enough CYA to bring it back up to 60 or so and I added it to my pool.

Now, it's been a few weeks and I'm pretty confident all the CYA granules have been absorbed. Also, my refill arrived quickly after I ordered it (thanks, duraleigh!) so I did a test. Result? CYA = 30. I know it's a subjective test and all, but what the heck? Was it zero when I had the pool store test it? If not, how did I see no increase?
 
Was it zero when I had the pool store test it?
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I'd say there's a decent chance of that. This forum is chock full of innaccurate pool store testing and it sounds like they may have completely missed it.

Because that test is so subjective, I'd do it one more time (and get another opinion) and insure you get the same number (+ or - 10ppm is about the best you can hope for)
 
I'll do another test this morning before I head over to the pool store to get more CYA.

I am algae-free. In fact, the water is clearer than it has ever been. My wife was just commenting a couple of weeks ago about the infinite underwater visibility we're enjoying this Summer.

When testing CYA, is it better to do it after the equipment has been running a while or does it matter?
 
I just retested and came up with these numbers:

FC 2.5
CC 0
Ph 8
CYA 30
TA 80

My Aquarite is running at 45% and the chlorine isn't high enough. Last Summer, it was running at 20% and keeping the chlorine a little too high. I'm guessing the low FC is due to the low CYA, so I intend to bring that up to 60-80. Also, my pH is too high and my TA may be a little on the low side.

I was surprised and pleased that the CYA test rendered the exact same result as it gives me some confidence in my testing methodology. I filled the tube until I had to strain to see the dot (I hope that's right).
 
bluenoise said:
I just retested and came up with these numbers:

FC 2.5
CC 0
Ph 8
CYA 30
TA 80

My Aquarite is running at 45% and the chlorine isn't high enough. Last Summer, it was running at 20% and keeping the chlorine a little too high. I'm guessing the low FC is due to the low CYA, so I intend to bring that up to 60-80. Also, my pH is too high and my TA may be a little on the low side.
Your high ph could very well be the reason why you are not generating enough chlorine. Your TA is fine, don't raise it. it could even be a bit lower. Where is your calcium hardness?
I was surprised and pleased that the CYA test rendered the exact same result as it gives me some confidence in my testing methodology. I filled the tube until I had to strain to see the dot (I hope that's right).
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You fill the tube until you CANNOT see the dot. Your CYA might be lower than you think.
 
I made some adjustments today, so I just retested:

FC: 2.5
CC: 0
pH: 7.6
TA: 90
CH: 230
Salt: ~3000
Temperature: 89 degrees

I added four pounds of CYA, so I'll test that again next weekend. That should put it up around 60, according to the Pool Calculator. I didn't realize I should leave the TA at 80 or lower, so that's why it's up. I added some baking soda a couple of hours after I added the muriatic acid for the pH.
 
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