CYA goes away...

[davelinde]

We have gone around this circle several times now... the pool runs fine, then at some point it won't hold chlorine levels. We have done the SLAM thing with some success, but a few times we have been told that CYA is low. We add CYA and the pool runs perfectly again.

Initially I know we had targeted the level to be on the low end (30 or 40) because I understood you don't lose CYA it usually ends up too concentrated. So the first time we added a few more pounds it seemed OK to me. It especially seemed OK when the FC immediately stabilized and all ran well. The next time we added a few more pounds had been after a long rainy summer... and again the FC stabilized right away and all seemed OK.

Now my wife came back from the pool store with a few more pounds of CYA again. When I asked her what the levels have been over time and what they are now she only knew that "CYA was OK" and now "CYA is too low"... so sorry - I'm without numbers at the moment. But am I right to be confused? Where does CYA go? If we add CYA and FC levels stabilize is that really an indicator we found the right thing to adjust?

 

[Smykowski]

How are you testing?

 

[duraleigh]

But am I right to be confused?

Yes, but the likely culprit is pool store testing. You know by now how we are ardent advocates of testing your own water.

If you ever decide to manage your pool with your own testing, a lot of your confusion will go away.

 

[jblizzle]

I agree. All you confusion is due to the apparent fact that you are not properly managing the pool chemistry by regularly testing yourself with one of the Recommended Test Kits.

If you are using the SWG, your CYA should be in the 70-80ppm range ... 30ppm is way too low for a SWG pool, especially in the summer.

 

[dschlic1]

Another way I have found to resolve this issue is to run my FC levels at 5 ppm or above with CYA in the 60~80 ppm range. This is a bit higher than recommended, however a very common issue is an infestation which eats the CYA which then lowers the FC levels. What ever the infestation is, it eats CYA quite rapidly and is tolerant of FC levels 3 to 4 ppm! To eliminate the infestation requires extremely high FC levels for very long durations. Interestingly enough I have found in my case poly quant algaecide works better than chlorine. I regularly add poly quant to my pool on a weekly basis.

 

[jblizzle]

Another way I have found to resolve this issue is to run my FC levels at 5 ppm or above with CYA in the 60~80 ppm range. This is a bit higher than recommended, however a very common issue is an infestation which eats the CYA which then lowers the FC levels. What ever the infestation is, it eats CYA quite rapidly and is tolerant of FC levels 3 to 4 ppm! To eliminate the infestation requires extremely high FC levels for very long durations. Interestingly enough I have found in my case poly quant algaecide works better than chlorine. I regularly add poly quant to my pool on a weekly basis.

What?
We have never heard of an "infestation" that consumes CYA in a pool (except for the rare occasions in a closed pool with 0 FC where a bacteria converts the CYA to ammonia). And certainly the difference between 3ppm and 5ppm should not have any impact.

If there is something growing in the pool, then you just need to follow the SLAM Process. And in no case is the polyquat really needed if the pool is decontaminated and adequate FC is always then maintained. The algaecide is really just insurance for if you let the FC get too low to slow the growth of algae.

To me it sounds like you need to SLAM the pool and then maintain adequate FC and there should be no reason for wasting money on a weekly algaecide.

 

[davelinde]

At the beginning of this all we got the better test kit so we can do an OCLT if needed. I think the same kit includes a test for CYA (not sure how many can be done though). My wife does the testing and has used the pool guy to confirm her numbers... and I think her numbers also show that CYA is "going away" somehow. I try to stay out of it and the pool water does look nice and clear so I have no reason to complain. Today I got curious and I was a bit dismayed when I asked her about the numbers and all she had was "too low" and "went down a lot"... She may actually have better records somewhere but I didn't feel like getting into an argument about it today. Still, I was curious if something (other than repeated systemic testing error) could explain it.

On theory I had was that what I think is evaporation could be a leak (we did have a leak before). But the pool has not lost more than an inch or so in the last 14 days so I'm thinking that's not likely or really even worth a bucket test at the moment.

 

[jblizzle]

A leak is about the only way for the CYA to drop considerably.
CYA is slowly consumed ... but experiments by Chem Geek (I think) only showed around 5ppm drop over 3 months if I recall correctly.

 

[duraleigh]

We have never heard of an "infestation" that consumes CYA in a pool (except for the rare occasions in a closed pool with 0 FC where a bacteria converts the CYA to ammonia). And certainly the difference between 3ppm and 5ppm should not have any impact.

If there is something growing in the pool, then you just need to follow the SLAM Process. And in no case is the polyquat really needed if the pool is decontaminated and adequate FC is always then maintained. The algaecide is really just insurance for if you let the FC get too low to slow the growth of algae.

To me it sounds like you need to SLAM the pool and then maintain adequate FC and there should be no reason for wasting money on a weekly algaecide.

+1 what jblizzle posted

 

[davelinde]

A leak is about the only way for the CYA to drop considerably.
CYA is slowly consumed ... but experiments by Chem Geek (I think) only showed around 5ppm drop over 3 months if I recall correctly.

OK - so if my wife does have numbers somewhere I can consider anything over 5ppm drop to be excessive and figure out how much water lost due to diluting would be needed to explain it that way. The other candidate is systematically low measurements?

I'm still wondering if we have some hidden organic cause here... but from what I understand (and I'm learning here) organic will explain FC loss but not CYA loss... while low CYA definitely explains the inability of a SWG to hold a FC level without any organic issues.

 

[jblizzle]

from what I understand (and I'm learning here) organic will explain FC loss but not CYA loss... while low CYA definitely explains the inability of a SWG to hold a FC level without any organic issues.

This is true. Organics could cause low FC regardless of the CYA level (which should not be affected). If the CYA is too low, then the FC could be low due to losses to the sun ... which in turn can quickly result in organics starting to take over.

Pool Store testing is notoriously bad ... ESPECIALLY at the CYA test.

 

[ping]

This summer my pool definitely lost more than 10 ppm of CYA a month, closer to 15 ppm. I did not lose any salt, so it was not due to losing water. My water temp was kept high, 86-90 degrees, and I also targeted the FC on the higher side due to lessons being taught 8 hours a day in the pool.

Do you keep the water temp on the higher side and is your FC target a little on the high side? I believe I worked it out that Chem Geeks numbers could lead to a 10 ppm or so loss. Then if you get an abundance of rain that could all add up to the CYA disappearing at a good clip.

Using your own test results with one of the recommended test kits and tracking them is the only way to be sure of the accuracy of your test results.

 

[jblizzle]

That is interesting. I think the CYA loss was related to the amount of FC maintained in the water. I wonder if the high use and thus likely more required chlorine could be why you showed a higher CYA loss?

And again I agree, accurate testing and records would go a long way to understanding.

 

[ping]

From what I gathered, you are right about the amount of chorine used leading to a higher amount of CYA loss than normal. We also ran the spa a lot at 100 degrees, but I'm not sure how much if any the water temperature contributes to the CYA loss.

 

[YippeeSkippy]

At the beginning of this all we got the better test kit so we can do an OCLT if needed. I think the same kit includes a test for CYA (not sure how many can be done though). My wife does the testing and has used the pool guy to confirm her numbers... and I think her numbers also show that CYA is "going away" somehow. I try to stay out of it and the pool water does look nice and clear so I have no reason to complain. Today I got curious and I was a bit dismayed when I asked her about the numbers and all she had was "too low" and "went down a lot"... She may actually have better records somewhere but I didn't feel like getting into an argument about it today. Still, I was curious if something (other than repeated systemic testing error) could explain it.

Are you sure that your wife actually is performing the test correctly??
Why not do some testing yourself and getting a better handle on how this all works?
All of the test kits suggested here have replacement reagents easily ordered and not very costly. Use that test kit and leave the pool man out of the mix!

 

[davelinde]

Are you sure that your wife actually is performing the test correctly??
Why not do some testing yourself and getting a better handle on how this all works?
All of the test kits suggested here have replacement reagents easily ordered and not very costly. Use that test kit and leave the pool man out of the mix!

The deal on building the pool (I just wanted a hot tub) was that I would help get it built and she would do the maintenance.

Once I start testing I know what will happen. She is very methodical and very smart - she'll figure it out.

The problem with the replacement reagents is that none of them are free and pool store testing is free! So there is a hurdle there. Of course - since we keep paying full retail for chemicals (we may not need) it is not hard to prove a return on investment... IF - we determine the pool guy is hosing his test.

 

[davelinde]

That is interesting. I think the CYA loss was related to the amount of FC maintained in the water. I wonder if the high use and thus likely more required chlorine could be why you showed a higher CYA loss?

And again I agree, accurate testing and records would go a long way to understanding.

So for sure we run the pool as warm as we can manage it with the solar heater, DW wants it warm.
Also, last time we got the CYA to "high enough" DW told me the FC was drifting up and I told her to adjust the SWCG... she had stepped it from 60% duty cycle down to 20% (lowest we can run it) and we were running the pump full out during daylight for the solar... and I think she mentioned the FC was holding a big high. So yes, we've run it at higher temps (90+) and higher FC (5ppm+) as we can.

So what I'm hearing is that there ARE mechanisms other than dilution that will change CYA?

 

[mas985]

Shocking reduces CYA:

degradation-of-cyanuric-acid-cya-t8880.html

 

[Smykowski]

The problem with the replacement reagents is that none of them are free and pool store testing is free!

You will get what you pay for. Financial reasons drove me to follow the book of TFP and preach from my sparkly pulpit. Take a look at my signature to see what I mean. I've got a 23000 gallon pool and I'm spending less than $30 a month on chemicals.

 

[zea3]

I have a couple of questions. Did you fertilizer your yard recently? Have you had heavy rains? Does your pool have and auto filler and an overflow pipe? Did you have a swampy pool at start of swim season?