TF-100 Cyanuric Acid Test Results

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
14,689
Tucson, AZ
#3
The test bottoms out at 30ppm. So if you have less than that, it would look like zero.

BUT, the test is meant to be done in outdoor bright lighting, not indoor lamp light. You should redo the test during the day. High noon sun works best. Back to the sun, tube at waist height, and only two fingers pinching the very top of the tube (you do not want to obstruct the entry of light).

Redo the test before making any chemical additions.
 

Akathisia

Gold Supporter
LifeTime Supporter
Jul 6, 2015
133
Davis, CA
#5
It makes a big difference. You want your back to the sun with tube down at your waist like JoyfulNoise advised. Under a can light or facing the sun the black dot can stay visible longer and give a false low reading.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
14,689
Tucson, AZ
#6
I did the test under a can light so don't think it will be much different but I will try it out. What is a desired level for a SW pool and is lower better or worse?
The two (sunlight versus a can-light) can not even be compared. A bright sunny day (in indirect sun) has a luminous output of nearly 11,000 lux (>1000 foot-candle) while standard indoor lighting has a luminous output of 150-250 lux. Even an overcast day has 4X the luminous output of a ceiling light (~1000 lux versus 250 lux).

The test should be done outdoors in bright lighting to achieve proper results. As for recommended levels, please see this Pool School Article - Pool School - Recommended Levels
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
31,394
Sebring, Florida
#7
and is lower better or worse?
Please read "The "ABC's of Pool Water Chemistry" up in Pool School.

The TF-100 takes a larger sample and has good resolution down to 20 ppm. The k-2006 goes down to 30 ppm