Which method to use for FAS-DPD Testing


Well-known member
Jun 10, 2020
Austin, TX
I was given link to the Taylor videos, using the FAS-DPD kit, and many of the videos have two ways of doing the test.
Method 1: Use the large tube to fill to 25mL or 44mL (in case of FC), then add appropriate number of drops of reagents
Method 2: Use the large tube to fill to 10mL, then add appropriate number of drops of reagent
Of course, method 2 uses way less reagents.

Is it ok to be using method 2 for all these tests (use 10mL sample size with appropriately smaller reagent levels), as it would save on chemicals use?
Or is method 1 recommended for all tests, and only use method 2 in case specific situations?

Here is link to the videos. Thanks for advice.


Gold Supporter
TFP Guide
Nov 12, 2017
Central California
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
10ml is fine, especially for FC. Because my TA is low (50-60) I'll usually use a 25ml sample for that. If your TA is high, then 10ml is good until it gets lower... My CH is around 400, so I always use 10ml for that test.


Gold Supporter
May 20, 2020
Katy TX
Pool Size
Liquid Chlorine
For FC testing - if you use the 10ml sample volume you can achieve accurate FC levels to 0.5ppm.
If you use 25ml sample (not 44ml) volume you can achieve accurate FC levels to 0.2ppm
So for a end result of 6ppm (for example) you would have added 12 drops of R-0871 for 10ml sample and for 25ml sample you would have had to add 30 drops. So the 10ml sample saves you drops but do you need to know FC to the 0.2ppm accuracy?
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