CYA Test

[kjsmom]

I have a 23,600 gal vinyl liner inground pool. On May 1st Leslie's tested my water. Results were:
FC: 1
pH: 7.6
Alk: 80
CYA: 30

That day, I added 5 lb 10 oz of CYA. Today, 5/9, Leslie's tested again:

FC: .5
pH: 7.8
Alk: 100
CYA: 35

My test results, with my drop kit, indicate pH of 7.6 and Alk of 80. I cannot test for CYA. My question is, would it be possible that the CYA is still not dissolved? According to Michael's calculator, 5lb 10 oz of cya should have raised the cya 30 ppm, to 60, not 35. The water temp is 71 -- not too bad. How subjective is the CYA test? I've read that a dot has to disappear; is the cya test predicated on a color change? Could the results be off by 30ppm? That seems to be alot for cya. Thanks.
PAT

[waste]

I have a 23,600 gal vinyl liner inground pool. On May 1st Leslie's tested my water. Results were:
FC: 1
pH: 7.6
Alk: 80
CYA: 30

That day, I added 5 lb 10 oz of CYA. Today, 5/9, Leslie's tested again:

FC: .5
pH: 7.8
Alk: 100
CYA: 35

My test results, with my drop kit, indicate pH of 7.6 and Alk of 80. I cannot test for CYA. My question is, would it be possible that the CYA is still not dissolved? According to Michael's calculator, 5lb 10 oz of cya should have raised the cya 30 ppm, to 60, not 35. The water temp is 71 -- not too bad. How subjective is the CYA test? I've read that a dot has to disappear; is the cya test predicated on a color change? Could the results be off by 30ppm? That seems to be alot for cya. Thanks.
PAT

Pat, there's obviously a discrepency in the tests. Did you add anything that would have affected the pH and alk? Why did you want to raise your cya?? (30 is IMHO about the perfect amount).

The cya test is VERY subjective! Any 2 people can run the same test, using the same tester, and come up with varied results (the trick to doing your own testing is to be consistant when doing your own, if you're a little off on your testing methods - at least you will be able to adjust for it and dose the pool accordingly)
Best advice; get a good kit, compare your results to a 'known' -i.e. pool store's (though if they don't calibrate their equiptment regularly, it's useless), and see how well you are performing the tests.

CAVAT- pool stores' computer programs seem to be designed to sell chems, so use your own knowledge to decide what to add (or not add) when they tell you how many hundreds of $ of chems to buy, to correct a ~problem.

[kjsmom]

I have a swg. This year I've decided to try following the Aquarite directions and get my cya up to the recommended 85. I know that's high and I'm trying to be careful not to go over 85. Do you think that I can assume that 8 days after adding the cya it has all dissolved? Is cya level a color type test or a digital computer readout? (I'm beginning to wonder if this particular guy at Leslie's might be color challenged.)
PAT

[JohnT]

Is cya level a color type test or a digital computer readout? (I'm beginning to wonder if this particular guy at Leslie's might be color challenged.)
PAT

8 days ought to be long enough. The CYA reagent clouds the water. The deeper you can see a dot at the bottom of the tube, the less CYA you have. The tube is graduated to read CYA level.

[kjsmom]

So --- Michael's calculator calls for 16 lb of cya to go from 10 (we had new water last Fall and only added some closing chems) to 85. I added 9 lbs in mid April. Then I added 4lb 6oz in the a.m. on 4/22 -- buy my husband backwashed in the p.m. so I assume that was washed out. Then I added the 5lb 10 oz on 5/1. Disregarding the 4lb 6 oz that was probably washed out, the remaining 14lb 10 oz should get me to 80 ppm, right???? I will take another sample there tomorrow and see if maybe they made a mistake. I think I will just trust that I know what has been added and see how well my cl holds. Thanks very much.
PAT

[CarlD]

Did you backwash your pool in the meantime? If you added the CYA and then backwashed in a day or two, you would have flushed all the CYA you put in back out.

Why do you want to raise your CYA from 30ppm? That's generally an ideal number. Now you have 35ppm, so why raise it more?

You could slowly raise it by using a floater with Tri-Chlor pucks--just watch your pH because it will drop.

Still our first recommended range for CYA is 30-50ppm. You are right there!

On to testing: I test my CYA levels myself. I do it the same way everytime, so deviations are from my own tests and changes are baselined from my own tests.

Establishing baselines and normal ranges for the test site is very common. Every lab that runs blood chemistry and hematology tests sends along its baseline and normal ranges. These can then be "normalized" in pharmaceutical clinical trials so they can be compared meaningfully to other labs' tests when the new drug is submitted to the FDA for approval.

[duraleigh]

Pat,

I think I will just trust that I know what has been added and see how well my cl holds.

That is a very wise decision. Pool stores notoriously don't test accurately. Get a kit that tests for CYA (Ben's is the best) and your pool chemistry management will become amazingly accurate.

[waste]

8 days ought to be long enough. The CYA reagent clouds the water. The deeper you can see a dot at the bottom of the tube, the less CYA you have. The tube is graduated to read CYA level.

John, I've seen some of your other posts, and I am inclined to trust most everything you say. Until today I would have agreed with your assesment of the solubility of cya - however, I went back to a pool I had added 5 lbs of cya to 8 days ago and I saw ~ almost all of it still sitting on the bottom. Maybe it's the cold water or lack of a MD in an 8' deep pool (however there are low suction ports at the bottom of the wall and a couple of 'low returns' which should be 'stirring up' the water down there). Not to say you are wrong but, empirically it looks like some pools won't take the cya as quickly as others. No biggie, some pools apparently need more time to absorb the cya
Just wanted other folks who still have the granuals in their pools to know that - they aren't the only ones

[JohnT]

I went back to a pool I had added 5 lbs of cya to 8 days ago and I saw ~ almost all of it still sitting on the bottom.

Wow. I'm surprised, but not shocked. There are differences in the way pool water works that I don't know if anybody fully understands. As a counterpoint, if I put CYA in a sock in the skimmer of my pool, it will be gone completely overnight from the sock (no holes ). I was amazed the first time I saw it happen. Testing indicated very close to the expected CYA change less than 24 hours after putting it in there.

[duraleigh]

Hi, Ted/John

We're sort of hijacking this thread but, yeah, I'm in the dark as to the wide variance as well. My last CYA addition of 11 lbs (35ppm) tested complete after 48 hours.......possibly sooner. I wonder if the age of the product has any effect.

Ted, what are you doing putting that stuff in the pool where the customers can see it? HIDE it in the filter!!! If they backwash, you get to sell them more!!