FAS/DPD test question

[Aaronbr]

With the FAS/DPD chlorine test at SLAM level, when do I stop adding drops of R-0871into the solution? The directions state to stop when the sample turns from pink to clear, and I was stopping when the solution at SLAM level changed from pink, but it was not exactly clear. It was more of a yellow tinge clear. The other day I stopped my test and left the sample sit so I could attend to my daughters needs at the moment and when I came back the sample had a pink tinge to it again. When doing the test at normal chlorine levels it's easy to get the sample back to crystal clear, but at the SLAM level do I stop when it's no longer pink or do I keep going till I get back to the crystal clear water sample again?

On a side note, I'm SLAMing again because I noticed cloudiness in my pool again and my OCLT didn't pass. I must not have gotten all the algae out of my pool the first time. This time I'm having a heck of a time passing an OCLT test even though I've kept my Free Chlorine between 30 and 35 for almost a week. I took all my lights out of the pool and spa as well as took all the drain covers off and scrubbed. I brush every night and I even took apart my filter to clean the grids as well as use a bleach water mix to brush down the insides of the filter housing best I can. I also scrubbed the skimmer and auto fill compartments. We are having higher than usual temps and I'm not sure if that is playing a part in my troubles, I often start to wonder if my autocover is causing an issue and someone needs brushed from the underside, lol. It kind of boggles my mind since I was still lowering my FC from the previous slam and was still above an FC of 12.

So I've kept my FC so high for about a week now because even though I'm measuring a CYA in the range of 55 - 60, two different pool stores I went to measured it 74 and 75. I figure I'd error on the higher side of FC even though I feel my test for CYA level is more accurate.

Before SLAM my test results were:
FC - 12.5
PH - 7.4
TA - 80
CYA - 60
Calcium Hardness - 450
Borates - 50
Salt - 3400

 

[Aaronbr]

Found my answer in the "similar threads" section below my own post. go figure.

Testing- FAS DPD test

Moved from here. FAS-DPD test question. When testing for FC I’m finding that sample turns clear at some point but with a few extra seconds or if I set sample down when I think it is clear it turns back to a light shad of pink. My reagents are several years old but seam fine? DPD powder a little...

www.troublefreepool.com

 

[HermanTX]

Always believe your own testing. So with CYA of 60, your SLAM level is 24ppm FC.

When testing FC, always continue the test until the solution is colorless. I use the word colorless as it may be clear but not crystal clear.

And you are correct, if you are testing and you let the solution sit after going to colorless it can turn back pinkish. So don’t add more drops to clear that.

 

[JRivers]

I'm not an expert on testing but here's my method. I add drops until the sample is clear. If I'm not 100% sure if it's clear I add another drop. If it gets more clear then I count that drop. If it doesn't then I don't count that drop.

I've left samples out for a while and it does turn back to pink after a while. I'm quite sure that doesn't matter. You're looking for the changes that happens in the first couple of seconds after adding the drop.

 

[duraleigh]

Walking away from most tests invalidates them Once you start you should finish.

On this and all other drops based test, hold the dropper vertical and allow the drops to form and then fall from the tip. Try not to squirt them out. Then you keep adding drops and counting until the LAST drop you add makes absolutely no color change. Subtract that last drop and that is the endpoint of the test

 

[Aaronbr]

Follow on question. I just saw the video on how to use the TFT Test kit and I use a much larger heaping scoop than in the video. I know that is ok, but for SLAM level testing, would someone still use the same amount of the powder as when testing normal chlorine levels?

 

[duraleigh]

Yes, The amount of DPD powder you use is largely irrelevant.