Which test kit?

[iwannapool]

How often would I see CL, CC or FC, above 15 ppm? I guess if you get a big problem CC could go high, but FC? By the way, what is FAS-DPD; is it an acronym or ?

[CarlD]

How often would I see CL, CC or FC, above 15 ppm? I guess if you get a big problem CC could go high, but FC?

If CC is over 15ppm you have a problem. But FC as high as 25? Sure.

If your stabilizer level (CYA) is over 100, you have to shock by getting FC up to 25ppm. You maintain your pool at something like 12-15ppm (I've forgotten exactly).

Unless you have very low CYA (20 or less) you normally will shock to 15ppm of FC--that's now at the limit of standard DPD kits. Past 15ppm ordinary DPD can bleach out and look like 0 ppm! Use FAS-DPD and you have lots of headroom.

[DavidD]

Here's another reason why:

A friend told me they kept having problems with bleaching of bathing suits and extremely dry skin but with very little chlorine in the pool towards the end of last season. A new bathing suit started to fade in less than a week. They were using a 3" puck feeder and would load it up but keep the dial turned down. He used the DPD test (not FAS-DPD) and wasn't registering any or very little chlorine when he did the test so he kept the feeder turned down to a low setting rather than turn it off or empty it. He knew he needed chlorine and theorized it was "burning off as fast as he could put it in". I brought my (Ben's PS233) test kit over and found he was actually over 30 ppm FC among other issues! All due to an old and in inadequate test kit.
Needless to say, he is using a better test kit (a bootleg clone of mine) and now even the BBB method....



Dave

[CarlD]

Here's another reason why:

A friend told me they kept having problems with bleaching of bathing suits and extremely dry skin but with very little chlorine in the pool towards the end of last season. A new bathing suit started to fade in less than a week. They were using a 3" puck feeder and would load it up but keep the dial turned down. He used the DPD test (not FAS-DPD) and wasn't registering any or very little chlorine when he did the test so he kept the feeder turned down to a low setting rather than turn it off or empty it. He knew he needed chlorine and theorized it was "burning off as fast as he could put it in". I brought my (Ben's PS233) test kit over and found he was actually over 30 ppm FC among other issues! All due to an old and in inadequate test kit.
Needless to say, he is using a better test kit (a bootleg clone of mine) and now even the BBB method....



Dave

I'll bet his CYA level was through the roof as well! I sure hope it wasn't a vinyl pool or that'd bleach too!

Saving money on test kits is a false economy. A FAS-DPD test kit will pay for itself hundreds of times over.

[DavidD]

I'll bet his CYA level was through the roof as well! I sure hope it wasn't a vinyl pool or that'd bleach too!

Unfortunately, they had just replaced the liner in the spring. Fortunately, it doesn't appear to have been adversely affected that "we can tell". And yes, his CYA was 100+ and pH read 6.8 but was obviously less. If I remember correctly, we dumped in 4 boxes of Borax


Dave

[CarlD]

Unfortunately, they had just replaced the liner in the spring. Fortunately, it doesn't appear to have been adversely affected that "we can tell". And yes, his CYA was 100+ and pH read 6.8 but was obviously less. If I remember correctly, we dumped in 4 boxes of Borax


Dave

Well, hopefully he didn't weaken it too much with that double whammy--too low pH (another adverse effect of pucks) and way too high FC. Both weaken the liner...he may get a year or two less out of it.

[chem geek]

The good news about his CYA being so high is that it helps mitigate the high FC. A 30 ppm FC with 100 ppm CYA is equivalent in disinfecting chlorine to 9.3 ppm FC with 30 ppm CYA or 0.4 ppm FC with no CYA. So while it is higher than normal, it isn't as damaging as it could be. Of course, with his reports of swimsuits degrading very quickly, it may very well be that his FC was even higher than 30 ppm. You can see how indoor pools without any CYA can very quickly degrade swimsuits with even modest 2 ppm FC. This is what my wife experiences with her swimsuits at our local community center -- they only last one winter season of swimming.

Richard

[waterbear]

How often would I see CL, CC or FC, above 15 ppm? I guess if you get a big problem CC could go high, but FC? By the way, what is FAS-DPD; is it an acronym or ?

DPD and FAS-DPD are the reagents used.
DPD is N,N-diethyl-paraphenylenediamine. It is the indicator used to test for clorine (and other halogens) using a color comparator. Most men have difficulties with this test because they cannot differentiate between the shades of red the test produces. The test can bleach out at chlorine levels above 10 ppm (which is not even shock level in most pools!). It is accurate to 1 ppm (IF you can differentiate the different shades of red produced.) It can test both free and total chlorine so combined chlorine can be found by the formula TC-FC=CC

FAS-DPD stands for Ferric Ammonium Sulfate -- N,N-diethyl-paraphenylenediamine
This test does not use a color comparator but is a titration test (like the tests for Total Alkallinity and Calcium Hardness) with a distinct endpoint color change from bright pink to colorless. Even people who are colorblind find this test easy to do. This test will not bleach out at chlorine levels as high as 50 ppm with an precision of as much as .2 ppm. (Comes in handy when you want to try and kill algae and it requires you to keep your FC levels at 15 or 20 ppm!) It test for free chlorine and combined chlorine directly. If you want to know your total chlorine it would be FC+CC=TC.

All things considered the FAS-DPD test is much easier to do and produces much more accurate results and is worth every penny extra it costs!

[iwannapool]

Thanks for all replies. Without an understanding of what's involved with these water tests it's hard to tell what you need and what you don't. Thanks, again.