Testing- FAS DPD test

[shockman]

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 crusted in container but dissolves okay. Searched on here for instructions with detailed testing which I’m sure I found before but did not find. Have not opened pool four 3 years lol
Marc

 

[shockman]

Thank you!

 

[mknauss]

Once the FAS DPD test goes clear, test over. Record result.
Reagents should be replaced no later than every two years.

Extended Test Kit Directions Archives

www.troublefreepool.com

 

[JoyfulNoise]

You should replace your reagents. The titrating reagent has likely lost some of its “strength” and you are probably adding more drops to get the sample to go clear than is actually needed so your readings are probably falsely high.

 

[shockman]

I’m trying to get replacement reagents but being in Canada that is not a cheap or easy or fast errand. Was mostly curious about the delay in the test returning to a very light pink. The Taylor distributor in Canada has obviously done a very good job of protecting the retailers. An example of the local pool companies mark up is the fact that it just cost me $100 for a jacuzzi face plate (small mouth)and 2 gaskets lol.

 

[JoyfulNoise]

The fading back to pink has nothing to do with reagent shelf life. Even new reagents do that. It’s a consequence of how the DPD indicator reacts with oxidizers and reducing agents. That’s why it’s important to do the test quickly and not delay between the end of the FC test and adding the R-0003 reagent for CC testing.

 

[shockman]

Thank you Joy, I found really good tips on tft site and ordered replacement reagents from them to ship to a buddies place in Montana. Summer lake house for him so not sure when I will get but in the meantime I’m believing my old reagents.