Sample Size for FAS-DPD test

[DanF]

Purchased the Taylor K-2006C recently and having been using the 25 ml sample quantity for testing FC and CC. Since the 25 ml sample requires more drops of R-0871 to determine FC, are there any downsides to using the smaller 10 ml size? Improved accuracy?

 

[YippeeSkippy]

Go with a 10 mL (cc) sample and one scoop of powder. Then count the drops and divide by 2. Voila! Fast, easy and saves on reagent use.

Maddie

 

[Haymarket]

I have the same question...I have been using the 10ml to save drops, but was wondering why the instructions call for 2 scoops of the powder regardless of whether you are using 10 or 25ml. Wouldn't one scoop work the same in the 10ml as 2 in the 25 as far as reactivity, since you are cutting the number of drops for the math proportionally with 10?

 

[YippeeSkippy]

One heaping scoop is enough for the 10 mL sample, two level scoops for the 25 mL sample.

Just like washing machine detergents, the manufacturers always advise you use the max.... so you'll be buying more! Shampoos say wash/rinse/repeat. Do you *really* need to repeat it??

Maddie

 

[IceShadow]

See discussion here:

DPD Powder Sensitivity for FC/CC testing

I've read that the exact amount of R-0870 powder isn't critical so long as the color changes. Given the apparent instability of my daily Cl readings, compared to what I was expected when computing daily SWG generation from its duty cycle, I decided to run a little experiment. I ran three...

www.troublefreepool.com

The powder is pretty cheap, and the Taylor scoop is smaller than the one with the TFT-100. So two scoops for 10ml is fine too.

 

[thefloatqueen]

Purchased the Taylor K-2006C recently and having been using the 25 ml sample quantity for testing FC and CC. Since the 25 ml sample requires more drops of R-0871 to determine FC, are there any downsides to using the smaller 10 ml size? Improved accuracy?

I always do the 10 ml sample. It will also save you money on reagent refills.
EDIT: I have the TF-100 test kit, if it makes any difference. ??‍

 

[Brianf60]

I have found the powder lasts a lot longer than the drops anyways. One good scoop and you should see a drastic color change.

 

[DanF]

I have the SpeedStir. I find that taking the magnetic bean out of the sample tube before adding the 10 ml of test water makes it easier and more accurate. Others find that?

 

[Wobblerlorri]

I have the SpeedStir. I find that taking the magnetic bean out of the sample tube before adding the 10 ml of test water makes it easier and more accurate. Others find that?

That's because the bean displaced some water and you're not really measuring 10 ml, more like 9 or 8 ml, depending on the size of your bean. You have to measure your sample first, then add the bean. I think Aristotle discovered that. One of those Greek philosophers, anyway.