Keep needing to add CYA - why would this be.

[wayner]

I have had my pool for about 7 years. It is about 100,000 L (25,000 US gallons) and has a Jandy Aquapure SWG. I have never had any problems with it. I have a paper cartridge filter so no backwashing.

This year I added CYA when the pool was first opened in mid-May (which is usual) and then again a couple of weeks ago I added about 2kg of CYA due to low readings. But when I take it to my shop to get tested the CYA is very low so I am now adding more. My chlorine readings have also been low so I have had to supplement the SWG with liquid chlorine. Is there any reason why my CYA would not stay in the pool? Normally I just add CYA at the beginning of the year and then I am ood.

The only thing that has changed this year is that I have added solar heating panels - the evacuated tube type. The guy who installed these for me has had some issues adjusting these properly and for some reason the solar panels seem to be allowing air to enter my system - it bubbles out of the jets. Could too much air (or Oxygen) cause issues with the CYA? Or is it getting burnt out by the solar tubes?

 

[Richard320]

I would suspect the test results are wrong before anything else. "But when I take it to my shop to get tested the CYA is very low so I am now adding more." I know your test kit choices are somewhat limited in Canada, but you should be doing it yourself.

Check out this thread -- pay attention to the CYA readings.

 

[wayner]

Ok, maybe my pool shop is not doing a great job. But low CYA correlates to my not having any enough chlorine in the pool despite the fact that everything looks fine with my SWG. And I know they are not overly accurate but my test strips also show low CYA. So you may be right but this means that two things - (1) my shop is totally screwing up the CYA test and (2) my SWG is not working. That isn't impossible but I would hazard to say it is unlikely.

And I am doing everything 100% the same as I have been doing for the last 7 years, except for the solar panels and I have always had a crystal clear pool.

But I will get a kit shipped to a relative in Texas to bring up to me as they are coming up for a visit soon.

 

[wayner]

My Taylor kit arrived today and I did all of the tests. The CYA was less than 30, and I have now added over 2.75kg of CYA to a 100,000L pool over the last month. So it doesn't look like the pool shop was crewing up the CYA test. Anyone have any ideas on why I need to keep adding CYA - as I mentioned above the only thing that has changed in my pool is that air is being introduced by the solar panels. Could this be causing an issue with CYA?

 

[PAGirl]

Do you have an autofill system?

 

[Casey]

Have you been getting a lot of rain?

 

[wayner]

No autofill and I haven't added much water recently. Some rain but not a ton.

 

[Casey]

Miscalculations on pool volume may be the culprit then. *shrugs*

 

[wayner]

But I have added over 5.5 lbs in the last month and I still get a reading of <30 (it appears that is the lowest reading you get with a Taylor kit). That is probably as much CYA as I added over the last 3 years. But I will be adding some more.

Is there anything that reacts with CYA that can cause it to dissipate?

edit - my pH was a little high at 8 when I did the CYA test. I have added some pH - and now have the pH at 7.5. Will that affect the CYA test? I haven't yet retested the CYA as my kit only came with enough CYA reagent to do a handful of tests and I don't want to waste it doing another CYA test now as I doubt anything has changed.

 

[PAGirl]

Are you holding any cl at all? Can you check for ammonia? (Visit an aquarium store for the testing supplies.)

 

[wayner]

I am holding some Cl but I have had to supplement the SWG with liquid chlorine. But I did start to get some algae growth a few weeks ago. In the last few days I am also having issues with my SWG but that is a story for a different thread.

What should I be long for with Ammonia? Too much? Will this dissipate the CYA?

 

[wayner]

I just read some threads on ammonia being generated by bacteria that was able to grow because FC was not present. I did have a bit of an issue with FC but I think I have that probelm fixed. I will continue to add more stabilizer and ensure that the FC is relatively high. I haven't cleaned my filter (paper cartridge) in over a month - should I do this before adding the CYA?

 

[RobbieH]

The filter won't have anything to do with algae or pool balance.

 

[wayner]

Could there be algae residing in the paper cartridges? SInce CYA is slow to dissolve isn't it also possible (or even likely) that if I add CYA to my pool that some of it may be sitting in the filter pleats. So if I wash the filter then won't I also be potentially washing away some of the undissolved CYA?

 

[RobbieH]

There could be algae on the filter, but not if the pool is properly maintained. If you think this is the case, you could soak them in a water/bleach solution. Just washing them would not be enough.

Depends on how you added CYA. If you hung it in a sock in front of a return, I don't think this is very likely. If you dumped into the skimmer, it is highly likely.

 

[chem geek]

If the flow rate through the evacuated tube solar panels is slow so that the water is very hot in them (perhaps later mixed with other water before coming into the pool so you don't get burned), then it's possible for the chlorine oxidation of CYA to be accelerated (though I would normally think the time to be too short). If this is happening, you would not only see a drop in CYA, but also an increase in chlorine usage. It takes 2.5 ppm FC to oxidize 1 ppm CYA. You've got other things going on right now in terms of possible algae growth so need to deal with that first, but after things are stable if you find that you have high chlorine demand only when the solar panel is operating and that this also causes the CYA to drop, then what I described is likely what is happening.

 

[wayner]

but after things are stable if you find that you have high chlorine demand only when the solar panel is operating and that this also causes the CYA to drop, then what I described is likely what is happening.

But this will be complicated by the fact that the solar panels only generate heat when it is sunny and doesn't the sun also cause the chlorine to burn off? I also only generate chlorine when the pool is running which is also when the solar panels are running as the pump currently runs from about 6am to 9pm which is when the sun is up.

But I guess I could control for all of this by shutting off the flow of water to the solar panels for a few days.

 

[chem geek]

Yes, you could compare running the solar panels vs. not running them. If your pool is uncovered, then the breakdown of chlorine from sunlight should be pretty much the same since the volume of water in the panels is negligible compared to the volume of water in the pool. Also note that the breakdown of chlorine from sunlight is independent of temperature. So comparing solar panels off vs. on would be very reasonable for comparing the FC loss assuming everything else is the same including the amount of sunlight (a cloudy day would invalidate your result unless that was consistent for all days of the experiment).

 

[wayner]

My pool is uncovered. The problem is that it is going to be hard to do a proper apples to apples comparison. Yesterday I added 1.75kg of CYA so I assume that will take close to a week to totally dissolve. So I should wait a week. The other issue is that I am getting intermittent error codes on my SWG so I am not sure if it is working properly.

 

[duraleigh]

I have only just skimmed this thread but I think I get the idea.....you are concerned that something mysterious is making your CYA disappear. It is not.

This time of year, splashout is about the only significant reduction in CYA like you are seeing. The problem is elsewhere....if I knew exactly elsewhere, I would certainly post it but I am stumped.

Is it the same brand each time you add? Is it 95% or more CYA?

I also think it is a mistake to let the solar panels into the equation......they have no significant impact on CYA loss.

"But when I take it to my shop to get tested the CYA is very low so I am now adding more."

Time and again, day after day, week after week, testing error by a pool store or the use of strips is the most common issue. I wish I could help you identify the issue but don't get sidetracked from the primary fact that CYA doesn't just go away.....something else is happening, I'm pretty sure.