How fast do pucks increase CYA?

[Xebec]

I have a Frog and only recently learned (from here) about the unfortunate side effect of increasing CYA. I'm using only the chlorine cartridge, not the mineral.

If I keep it on a fairly low setting (say 1), can anyone give me a rough idea of how long it takes to start having a signficant effect on on CYA? For example, could it increase it from 50 to 57 in a single week? What if it were on a higher setting?

I'm wondering if I might have misread the CYA test in my K-2006. (Judging exactly when I can no longer see the black dot is a bit iffy for me.)

 

[frustratedpoolmom]

Give this a check out....

http://www.taylortechnologies.com/Chemi ... ntentID=44

How are you using the bac pacs without the mineral cartridge to hold it in place?

Someone posted a percentage on here, I don't recall the exact amount....it's a bit more unreliable because there is an undetermined amount of tri-chlor in those bac pacs. It's not as easy to say "one puck contains X amount of CYA." Theres lots of little trichlor tabs in there....and those pacs and/or frog can malfunction and lead to the dissolving of the tabs in days instead of weeks. I'd be weary of continuing to use it. JMHO.....

Do you have a SWG? Otherwise your CYA is fine and I wouldn't use the trichlor and add any more CYA.

 

[chem geek]

Regardless of the concentration of Trichlor in the packs, for every 10 ppm FC added by Trichlor it also increases CYA by 6 ppm. So if you know your chlorine usage per day or if the packs you are using give some sort of chlorine dosage, then you can figure this out. Typical pools exposed to sunlight use around 2 ppm FC per day (some more; a few less). At that rate, this is an increase in CYA of 36 ppm per month. Of course, the CYA gets diluted through splash-out and backwashing, but not that much unless the pool volume is smaller.

Richard

 

[stevenbrla]

chemgeek,

I certainly don't have the knowledge (or inclination) to disagree with you, but assuming your numbers are dead on, why would the manufacture of these pucks intentionally "miss the mark"?

just curious to your extended thoughts...

thanks,
steve

 

[JohnT]

My experience has been 7.5ppm per week in my own pool, which given the uncertainty of the CYA test seems very much in agreement with Chem Geek's number.

 

[Guest]

chemgeek,

I certainly don't have the knowledge (or inclination) to disagree with you, but assuming your numbers are dead on, why would the manufacture of these pucks intentionally "miss the mark"?

just curious to your extended thoughts...

thanks,
steve

I assume by 'miss the mark' you are asking why do these pucks contain CYA. Trichlor (which is what these pucks are made of) is a chemical made from CYA and chlorine (as is dichlor). The reason trichlor is used in erosion feeders is because it is a very slow dissolving form of chlorine. All other forms of solid chlorine dissolve MUCH faster and are not really suitable for erosion feeders (although there are some speciality feeders for dichlor and cal hypo out there--their lack of popularity is a testament to how poorly they actually work). Bottom line is this, all stabilized forms of chlorine (trichlor and dichlor) will cause CYA levels to rise over time. Dichlor actually adds CYA faster than trichlor (Dichlor adds 9 ppm per 10 ppm of FC while trichlor adds 6 ppm per 10 ppm of FC. Makes sense when you realize that dichlor has two chlorines attached to the CYA in the chemical while trichlor has three chlorines attached to the CYA.)
Some pools can run on trichlor without problems but these are often smaller pools with sand filters that are backwashed on a regular basis (which causes a larger water replacement in relation to total pool volume) particularly in climates that have a short swim season and that winterize pools (which involves draining more water out that gets replaced when the pool is opened.) The worst case scenario for trichlor use is in a climate with an extended (5 months or more) swim season that does not winterize pools AND uses a cartridge flter or a non backwashing DE filter. In these cases, particularly with a smaller pool, it can go from 0 ppm CYA to way to much in the period of just a few months and often the pool reaches 'critical mass' and starts having algae outbreaks during the height of the swim season.

 

[chem geek]

Steve,

Ditto to what waterbear posted. I am also confused by "miss the mark" since I don't think any manufacturer of products that have Trichlor or Dichlor, including the Frog, has ever put on the label or any instructions anything indicating the amount by which the product will increase CYA levels. In my opinion, this is deceitful (intentionally withholding materially important information a consumer would need to know in order to make an informed purchase decision), but it's been this way ever since these products were introduced to market. As waterbear noted, these are chemical facts, not just speculation. Trichlor isn't a "mixture" of separate CYA and chlorine -- it's a molecule that contains both in EXACT proportion. Trichlor is shown here, Dichlor is shown here and CYA is shown here.

Richard

 

[JasonLion]

To put it another way, it is important to realize that disinfecting chlorine is inherently unstable. There are very few things you can combine it with that don't deactivate it's sanitizing ability. Of the six known reasonably stable forms of disinfecting chlorine, one is a poisonous gas, two contain CYA, one contains CH, one is quite expensive, and the last one is bleach.

 

[Rob]

In my experience, over the short 3-4 month swim season here in Canada, our CYA will raise about 15-20 or so. We backwash fairly infrequently (maybe once every month), and have very little splashout, but we generally keep our FC levels fairly low.

Interestingly, we don't really drain the pool much to winterize it, and in the fall, our CYA is around 50, and in the spring, it is 0. I think there is something that happens here with the cold winter that takes care of the CYA (we can use our pool as a skating rink for the winter).

Each spring, we add around 30 ppm CYA, and finish off the year around 50, so for us it works out just fine to use the pucks. But every pool is different, and we do watch it, with the backup plan to switch to bleach if we ever had to due to high CYA levels, but so far that hasn't really been a problem.