TF-100 vs Colori Meters

[ItsUncleBob]

Hi Friends,

I love the TF-100 with SpeedStir, But I'm not sure if I'm making mistakes testing or store tests are just wrong.

So I took sample of water two two stores that use automated machine.

Their results:

Store A:

pH 7.9
Hardness 91 ppm
Alkalinity 92

Store B:

pH 8.0
Alkalinity 83
Hardness 95

TF-100
ALK 60-70 ( it got more blue after 7th drop not sure if it counts ? ) 8th was no change
CH 125 ( maybe 120 )

I will stick with TF numbers and not add any Calcium ?

Thank you

 

[mknauss]

Don't take your pool water to pool stores. Just confuses things. Trust your best residential test kit made.

 

[ItsUncleBob]

Question I re tested calcium today and now I get blue on 3 maybe for drops ....

I did test twice in a row... Prior tests were showing reading of 125 ... Can high pH impact calcium test ?

Additionally I added bunch of acid to move pH down, it worked but my TA is still in 60-70 range, acid should moved it down

Not sure why my test with TF-100 are not consistent

Any suggestions, thank you

 

[HermanTX]

This confirms my theory - having too much of any thing only confuses us - a person with 2 watches never really knows what time it is. Best to stick with your own testing and do it every day - even twice a day to practice. This will help drive consistency and competence.
I mark each of my bottles with a sharpie with how many drops each is to have (this is for reagents that have fixed drops as part of the test). This way I can always check myself that I am following the process. Also, hold the bottle vertical (not at 45 degree angle) to get consistent drop sizes. If your result is not as expected - then do the test again - from scratch. Rinse the tube, dry it, and put in pool water. In the TF-100 test kit, the chlorine and calcium test use 10ml samples and the alkalinity test uses 25ml pool water samples. Mixing that up can cause chaotic test results. Just go over every part of the test again to ensure you are following process. Also, is your sample pool water coming from about 12-18 inches of depth in pool?
I have set my TF-100 test kit up to ensure I do not mix the wrong reagents. See picture
Bottom left is CYA, bottom right is Chlorine
Middle row is Calcium from right to left (speedstir is on far left)
Top row is Alkalinity from right to left.
I use dedicated tubes for each test and dedicated spinner for each test.