Bad CYA rumors real or some other reason for CYA not rising?

[Opus4]

I spent some time searching/reading more on this forum about CYA and possible reasons for it not to go up after adding it -- I've seen comments about losing CYA via water loss (not happening), bacteria converting the CYA to ammonia (don't think that's happening), and a few comments referring to rumors of possible bad batches of CYA (seems possible).

History: When using a solar cover, my pool uses no more than 1 pint to 1 quart of 6% bleach daily. This has been fairly steady. Since it has been too hot to leave the solar cover on, I've been adding more chlorine to make sure FC doesn't go too low after the pool being in full sun all day (no shade at all until the evening). In full sun, I end up using ~5 quarts of 6% bleach daily. After killing off algae from my steps a few weeks ago, the steps are still out & CC is usually 0, but sometimes 0.5 (barely pink) daily. Water is just about glass clear. When I put the cover back on, bleach usage immediately returns to 1 pint to 1 quart. FC has not tested below 4 for the past couple weeks.

My CYA was testing under 30, so I decided to add more. After adding a couple pounds via socks in front of the skimmer, I waited almost two weeks & now the CYA still tests as under 30 & thus hasn't changed. I have the 50ppm CYA standard solution from TFTestkits & confirmed that my testing method resulted in a ~50 ppm reading, so I don't think I'm testing wrong.

I don't think this qualifies as bacteria converting the CYA because Cl usage only goes up when the pool is uncovered in full sun.

Question:
Am I missing a reason for the CYA not to budge? It just seems to me like the CYA I have isn't doing much of anything.

The CYA bucket is Nu-Clo brand. I'm tempted to buy some from a different pool store & try that instead of wasting time adding it again & waiting to retest. Now that I think about it, I remember adding 4 lbs of CYA this spring from the same store because of starting with fresh water after the installers fixed a liner issue from last summer's install & that resulted in the initial CYA reading of under 30, which is off the expected 40+ value from the pool calculator.

 

[JasonLion]

Check the labeling on your CYA container. Some companies sell products that are only 50% cyanuric acid, instead of 97+%. If you have one of those it would account for your experience.

It is also possible that some random CYA testing error combined with the pool holding a bit more water than you think it does could maybe account for it, though that doesn't seem particularly likely.

 

[Opus4]

The label says 100% cyanuric acid. I saw no lot number, so it is hard to track that, btw. One interesting experiment would be to add the CYA to our reverse osmosis drinking water to see what a subsequent CYA test says.

I'm basing the 11K gallons of water on the pool calculator's result for my 15x30 oval pool at ~ 45 inches deep. That value roughly matches other volume calculations I did in the past.

My wife just reminded me that we have a bucket of trichlor tabs from the pool installation, so I think I'll try them for a week or so to see if the CYA goes up.

 

[Bama Rambler]

It seems to me that we have had a lot of reports of people adding CYA this year and not getting the reading they expected. If you have some of the CYA left it would be an interesting experiment to see if adding a little to a 5 gal bucket if water gave the expected result. If you do it, please post back and let us know how it turned out.

1/4th teaspoon of CYA should be about 60ppm in 5 gallons of water.

 

[anonapersona]

I was hoping someone would post the measurements needed to do that test.

 

[Opus4]

1/4th teaspoon of CYA should be about 60ppm in 5 gallons of water.

Thanks -- that helps confirm some calculations I did last night.

I'm assuming I need to give it time before testing. Oh, and I'll test the water I start with before adding it too.

As a side note, the trichlor tabs practically effervesce -- they are small "One-A-Day" tabs from Nu-Clo, weigh about 3.2 oz & say they are 66% trichlor. Just commenting because they must be different from the larger tablets used in a floater.

 

[Opus4]

Having started this CYA test, I have to say that getting the stuff to dissolve is an interesting experiment of its own. While I can tell there is less of the CYA granules visible in the water than the 1/4 teaspoon I started with, some of it is still swirling around the water after 2 days & stirring a few times per day.

 

[Opus4]

Well, I think it has been long enough to test the results. To recap: I dissolved 1/4 teaspoon of CYA starting on the 26th. It all looked to be dissolved & mixed into 5 gallons of water. The expected CYA reading would be approx. 60 ppm.

I first tested the tap water. As expected, there was no cloudiness at all; CYA should be read as 0.

I tested the sample solution multiple times with 2 separate reagent mixes a couple hours apart. The first time, I consistently saw the dot disappear between 30 & 40, but closer to 30. With the 2nd reagent mix a couple hours later, I consistently saw the dot disappear between 20 & 30, closer to 30.

This was a ways off from the expected 60 ppm, but there are air pockets between the CYA granules in the 1/4 teaspoon measurement and perhaps while it all looked to be dissolved, maybe it could have sat for another few days.

In short, the CYA I bought is CYA. It tested lower than I expected, but I think there could be reasons for that.

The pool water, however, still tests below 30, as if I hadn't added any of the CYA and I don't know why that would occur. (And, yes, the 50 ppm standard from TFTestKits still tests as around 50 for me, so my results shouldn't be tester errors.)

 

[anonapersona]

If possible can you keep the bucket of mix for a few more weeks? I am still wondering if it just takes a lot longer than the week we have been expecting.

 

[Opus4]

I haven't dumped it yet, so I can try leaving it for a while. I should probably add some chlorine to it if it is going to sit longer.

But, it has been a few weeks since I added the CYA to the pool & that still hasn't budged.

I've only added a few of those quick dissolving trichlor pucks so far because the weather cooled a bit & I put the cover back on, causing the chlorine demand to go back down.

 

[Opus4]

Since I said I would let the 5 gallon bucket sit a few more weeks, I thought I would finally report the results... unfortunately, I failed the test. The CYA test of the water on the bucket resulted in perfectly clear water in the CYA tube. I had been putting small amounts of bleach in the bucket, but obviously not enough as something grew in the water & the CYA that was there is gone now.

As for the pool: after the 2 lbs of 100% CYA I said had been added earlier + the more recent addition of 15 quick dissolving trichlor pucks, the pool water CYA test results in 30 ppm. That's barely up from the less than 30 I was getting. I have no explanation for this, unless whatever grew in the bucket & ate that CYA can also survive & eat the CYA in the pool even with the higher level of Cl in the pool -- I've been keeping FC above 4; in fact, I don't think it has ever tested below 4.5 since my last post here. (I've been putting in a bit more Cl the last few weeks because I thought the CYA additions would have brought it up to at least 40.)

And, yes, I tested the 50 ppm CYA sample at the same time today so I could be sure to test all samples the same way.

 

[Bama Rambler]

That is very interesting, puzzling but very interesting. Thank you for posting back about this.

 

[Pontiac]

I think you need to start bottling your pool water and selling it! I have a bunch of pools I need to lower the CYA level on. :-D

 

[Opus4]

I think you need to start bottling your pool water and selling it! I have a bunch of pools I need to lower the CYA level on. :-D

Sure, I could do that. Just be aware that the water might evaporate during shipping and you might only end up with dehydrated water. Just add more water when you get the container & you'll be fine.