CYA Testing

[yann]

Hi all,

As usual I am really confused about CYA and testing.

I haven't added any CYA to the pool in the past 8-10 months or so (last Australian summer)
Back then I was pretty confident my CYA was 70-80.

Since then there has been lots of rain, back washes, etc...
So it would be natural to expect a drop in CYA.

I have tested, re tested, tested again, with different samples, new reagent, precise measurement 50/50 pool water / reagent with graduated syringe: my results show a CYA of 90-100 !!

Very confusing, so out of interest I took my water to the shop and 3 different shops gave me a reading of CYA 40.
I know about shop testing, but they all gave me identical readings which are in line of the logical drop in CYA over the winter.

Any advice??
I do not want to adjust my FC on a guesstimate of my CYA.
I've been keeping my FC at 7-9 in case my testing is accurate, but if my CYA is truly 40 there is not only no need to keep the FC that high, but i might want to increase to 60-70 for the summer.

Thanks all

 

[Jimrahbe]

yann,

How are you testing your CYA?

I too would suspect your CYA is 40 ppm... If true, that means your testing method or your test kit is the issue.

If you were only off 10 or even 20 ppm, I could understand, but your measurement is off way too much. Not sure what is wrong, but something does not add up..

Do you have any friends that have a CYA test kit? If so, I would have them test your pool and see what they get... I would also compare what you get when testing their pool water.

Thanks,

Jim R.

 

[Bvacchiano]

Fill to 90. If u see dot good. Dump back into bottle. Fill to 50. If you don’t see dot GREAT. You have a CYA of 60-80. Call it good. Keep FC at 6. That’s what I do anyways. I’ve learned my lesson of trying to nail down the “exact” CYA. I’ve never had to SLAM yet.

 

[yann]

Hi guys

Thanks for the replies.

JR
I test with Clear Choice Labs (https://www.troublefreepool.com/members/131789-BrettClearChoiceLabs), the best you can get in Australia. Based on Taylors, very similar to TF100. Brett can shed some technical light on his products if needed.
I do have a standard CYA test solution calibrated at 50ppm, and I test it at 50ppm.

For my pool water I mix 5ml of pool water with 5ml of reagent. Mix for 30 seconds. Let it rest and come up to temperature. I usually do the other tests while CYA rests. Then mix again for 30 seconds and then conduct the test. Fill to 100ppm and check. If i can see symbol, I fill to 90 and check, so on and so forth until symbol goes away.
Unfortunately I do not know anyone around doing their own testing. They're all pool shop testing (and balancing of course), and yet they do not seem to have any issues with their pools.... But that's a different topic, with probably millions of posts about it on this forum only!!

BV
That's a good method and I would agree with you that I don't want to nail the exact CYA. I'm happy to know I'm in the 60-80 range. It's just I didn't expect to test at 90ppm when there has been no CYA addition for over 10 months, and my CYA was 80ppm last summer.

Any more advice??

I suspect my CYA is closer to 40 than 90, but I don't want to add CYA until I'm sure of my current level, and I want to know my future tests will be accurate

Thanks

 

[Costas > DownUnder]

Any more advice??

Have you tried measuring the included CYA 50ppm standard to test your overall process...?

I assume you are testing on a sunny day (or under a very bright light) with your back towards the sun and vial at waist level etc?

If you test the standard and it measures in at 50ppm then I would be believing your test kit and not the pool store(s).

 

[Jimrahbe]

yann,

A real puzzle... Logic says that after 10 month, a lot of rain and no CYA additions, it seems unlikely that your CYA would go up...

On the other hand, if you can test the standard and come up with 50 ppm, then your reagents and testing technique must be correct.

Based upon your feedback, I agree that you should trust your own testing..

It would be interesting to dilute a sample of your pool water by 50% and take that same sample to the pool store and see if they say it is now 20 ppm or do they still measure 40???

Please let us know how all this turns out...

Thanks,

Jim R.

 

[Leebo]

I quickly skimmed the thread and may have missed it. What’s the water temperature?

 

[yann]

Hi again

That's what puzzles me, reagent and technique seem ok since standard solution tests at 50ppm....

I'll try the dilution method, thanks

Pool temp is currently around 24oC - 75oF

 

[AU Pete]

I have had erratic results like this from the Clear Choice Labs CYA test kit. Like a pool water test of 50 one week, then 100 just 2 weeks later after not adding any stabiliser. I believe they changed suppliers at some point and the test was supposed to be much more stable - but I am still getting weird results. Brett from Clear Choice Labs has always been super helpful - but I ended up just having to try an alternate test. Perhaps Brett will chime in here if there's any more news...


I ended up switching to the blue devil kit from direct pool supplies (https://www.directpoolsupplies.com.au/cyanuric-acid-stabilizer-cya-test-kit) for CYA specifically and it has been much more stable for me.


I hope this helps - the CYA test is still the one that causes me the most concern


(though through the help of this forum and the CYA/FC relationship - I’m now up to almost a year with zero algae so must be doing something right


Pete

 

[yann]

Thanks Pete.

I used 2 different bottles of reagent with different lot numbers.

Both standards solutions tested at 50ppm the way they should so I would assume reagents and testing technique are ok, and still getting unexpected readings with pool water.
So unless the neighbours have been throwing CYA over the fence into the pool, I really can't explain the readings

Maybe I'll try DPS kit. I get my DE from them and I'm running low, so I might place an order for both and give your Devil test kit a go!

Thanks Pete

---Update---

Those DPS Devil CYA kits are no cheap!! Twice the price compared to CCL. How many tests do you get out of a kit? I've had my full test kit from CCL for 15 months and still using my original CYA reagents, only just cracked open my last bottle to double check my results.

 

[AU Pete]

Those DPS Devil CYA kits are no cheap!! Twice the price compared to CCL. How many tests do you get out of a kit?

i'd estimate 6-7 tests. so 1-2 years depending on how much rain you get (and have to backwash) ... so yes ... not cheap


I can't explain the irregularities either - but I have noticed *sometimes* that I'll get a very different reading from the CCL CYA kit after backwashing (and this is weeks after adding stabiliser). So maybe backwash - and then test with the CCL kit a few days later... it would be an interesting data point


(I don't use DE though - so not sure if that messes up your backwash routine)

 

[yann]

To be honest I don't backwash very often.

I do a deep clean of the sand filter at the beginning of the season, and only backwash when pressure is up 25% of the nominal pressure, which is probably 2-3 times a year.
I need to add DE every time I back wash, so if I just need to empty the pool following heavy rain, I just dump direct to the drain, bypassing the filter.

I'm not sure how backwashing could affect CYA, unless you CYA is somehow "trapped" in your filter and then gets "released" during back wash operation. Maybe if you dumped the CYA powder direct into your skimming basket and CYA gets stuck in the sand with no chance of dilution.

Not my issue anyway, at least I don't think so

 

[AU Pete]

I'm not sure how backwashing could affect CYA.

sure - to confirm, I don't think backwashing was affecting the actual CYA - but it seemed to have some effect on my misbehaving CCL reagent / test result - so in the back of my mind I was wondering if there was something *else* in the water that was setting off the CCL reagent and causing it to read over/under. But I really have no idea

 

[Jezza]

Yann- a mystery for sure.

Notwithstanding that your standards are testing true and with the use of different batch numbers it would seem to rule out testing error or dodgy reagent. I am thinking that perhaps your CYA could have been a little higher than what you originally thought when you last tested before the winter. You mention minimum backwashing over the winter so perhaps you didn't lose a great deal in that regard (plus the small bit you tend to lose over winter) could have made the total CYA loss minimal.

In any case, I would tread cautiously with the further addition of CYA. Perhaps test for CYA every couple of weeks from here and see if you tend to see a consistent pattern. Keep the FC level elevated for the higher CYA level.

 

[yann]

Thanks Jezza


Weather not great for CYA testing at the moment.
Will start fresh again in a few days once the storms have passed.
A bit of rain dilution might help with the readings.

Won't add anything until i'm sure. Got caught in the past and high CYA levels really don't work in my pool, algae bloom too easily so I need to keep my FC at 10% CYA to be sure.

I'll post back again a few days.

Thanks for your help every one

 

[yann]

HI all

Re tested today, with Standard solution first to make sure my technique was good.
Then tested pool water at 50-60 ppm, did 10 consecutive tests and got 50% on either 50 or 60ppm
I believe the rule is to consider the higher result as the true result.

So I'll call it 60ppm CYA!
Yay!
That makes sense now.

To raise my CYA, I've got some left over TriChlor tablets. Should I use them? 1x200g tablet raises my CYA by 3ppm according to Pool Maths, so 3 tablets should do the job.

Ot just get normal CYA from the shop and add 365g according to pool maths?

I'm after a target of 70ppm CYA.

Thanks

 

[AU Pete]

HI all

So I'll call it 60ppm CYA!
Yay!
That makes sense now.

Thanks

cool. just to confirm - did you end up getting a different test kit/solution from the beginning of the thread? at the start you were getting a CYA result of 90/100 with the CCL test

 

[Costas > DownUnder]

To raise my CYA, I've got some left over TriChlor tablets. Should I use them? 1x200g tablet raises my CYA by 3ppm according to Pool Maths, so 3 tablets should do the job.

Yes you can use them if you have them lying around.

 

[yann]

cool. just to confirm - did you end up getting a different test kit/solution from the beginning of the thread? at the start you were getting a CYA result of 90/100 with the CCL test

Hi Pete

Same kit.
I know, strange...
Maybe something wrong with my eyes on the day.
I should say I did brush my test tube inside & out with a small toothbrush, dunno if there was any residue that was blocking the light.... This is all theory.

Still, I can't believe there is no genius chemist out there capable of developing a reliable & reproducible test for CYA, considering CYA testing is the core of the TFP method, based on the CYA/FC relationship.

So many factors can affect the results: pool water temperature, batch quality of the reagent, a mini cloud passing by the sun, too many beers the night before, etc.....

- - - Updated - - -

Yes you can use them if you have them lying around.

Though so, thanks mate