CC and the TF-100 test

[napkin41]

Hi all,

I just wanted to understand the CC test for the TF-100 kit.

It seems to me that since the kit only reads chlorine in .5 intervals, you can never really be too sure if you're at the ".2" mark. I think the obvious answer is if the solution turns any shade of pink after adding 5 drops of R-0003, and goes clear after the first drop to measure the amount, it's probably time to SLAM? (And, obviously, if it takes more than a drop to determine CC level, it's definitely time to SLAM.)

My water remains clear even after the 5 drops, but I guess my question is, given a properly maintained TFP pool, and an average swimmer load during the summer, what is your typical indication that it's time to SLAM? (Would you wait if the solution turns only the very slightest shade of clear-pink after adding R-0003?)

Thanks again!

 

[AftonJeeper]

You can use a 25ml sample and multiply by .2.

There isn't normally any reason to do this, but if you need more precision you can do this test with a 25 ml sample of pool water and multiply the number of drops by 0.2. In most situations the added precision is useless and simply wastes reagent.

From here: Pool School - FAS-DPD Chlorine Test

 

[napkin41]

You can use a 25ml sample and multiply by .2.

Thanks AJ. And thanks for the reference. Judging by the literature, it sounds like this is "universally considered a bad move." To all you pros the question still stands. Without wasting reagent on a precise test, what's your typical indication that it's SLAM time? Or, do you go through the effort to precisely measure CC to see if it's above .2?

 

[JamesW]

If the pink clears with one drop at 0.5, you're fine. Maybe elevate the fc a little but a full SLAM is not necessary.

Perhaps do an OCLT if you think something might be starting.

Typically, going to an fc/cya ratio of 15% for a day or two clears any problems before they start.

 

[napkin41]

Thanks JamesW. I think as I transition to the TFP method, I'm still trying to shake off the more traditional pool care school of thought. I was under the impression that, come summer time, as my family enjoys the pool and inevitably creates a CC load, SLAMming (the "weekly shock") would be required to take those CC's back down to zero.

It sounds like I misunderstood. Maintaining target FC for CYA, or elevating it perhaps to 15% when needed, should take care of any CC's that are generated throughout the season?

Thanks!

 

[Texas Splash]

what's your typical indication that it's SLAM time

The TFP Pool School - SLAM - Shock Level And Maintain page states, "If you have algae, or the CC level is above 0.5, or the free chlorine (FC) level is zero, you should SLAM the pool." I emphasize "should" because there are a few unusual times where someone's CC may be elevated due to something added to the water.

But here are a few other indicators:
- Green anywhere or green plumes when brushing
- Cloudy water with filter PSI increasing quickly
- FC dropping quickly or more than 4ppm in 24hrs with no large swimming load or other explanation
- Organic staining

I'm probably forgetting an item or two at the moment, but you get the point. And remember, the CC test performed with the FAS-DPD test is very good, but sometimes our water just needs a little boost of chlorine to help it through a tough day or two. Maybe pollen or some other local products made it to the water to generate some concern. Sometimes the lack of sunlight might impede oxidation and effect your water's results. You learn more about your pool and its water as time goes on. Just like a parent, you know when something's off, and that's the great thing about TFP - testing your own water and making immediate changes as required to maintain it crystal clear.

Like JamesW said above, as a consistent TFP maintainer, a simple increase of FC for a day or so might just be enough to resolve those CC concerns.

 

[napkin41]

I re-read the article and I see now that I was confused about the need to shock weekly.

Thanks for setting me straight!