Hot tub chlorine test using DPD.

JillKC

Silver Supporter
Aug 23, 2019
19
Fredonia, NY
Pool Size
17000
Surface
Vinyl
Chlorine
Liquid Chlorine
We have a small 350gal hot tub. Using the frog floater for chlorine and BB for TA /pH. When I check chlorine using the FT-100 kit, the water typically stays red or goes clear for less than a minute and returns to red. It reads low to normal when using R-0600. A test strip appears normal. Is the DPD just not intended for hot tub water? Is there a different process for tub water vs pool water? Insights? Thanks.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,613
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
When I check chlorine using the FT-100 kit, the water typically stays red or goes clear for less than a minute and returns to red.
This sounds a little confusing so let's be sure. With the TF-100, you should be using the FAS-DPD (powder & drops) to test your FC level. It should start as a bright Barbie pink when you add the powder to indicate you have chlorine. Then you stir and add drops until it goes clear and divide that number in half. That's your FC level. Then go immediately into the CC test (if performed) or just discard the solution. If you let the clear solution sit, it will just start to change back to a light pink.
 

phonedave

Well-known member
May 30, 2012
1,016
Montville NJ
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
The @Ease or Frog system does not use "normal" chlorine. It does not work with a normal FAS-DPD test. It will show low FC and insanely high CC if you try to use it,
 
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