Faulty Test Kit Components Causing Inaccurate Readings?

[chuckp]

Good Morning,

Once again, I am grateful for this site in helping me maintain my pool.
I am using a TF-100 test kit:
1. I opened the pool on 5/3
2. water was way low, so I filled it overnight
3. 5/4 : added 1.5 packs HTH Shock
4. 5/5: readings FC = 7, TA = 20, CYA = 0
5. added chlorine, baking soda, borax, and cya based on pool math
6. 5/6 : readings: FC = 23, PH = 7.6
7. 5/7: readings FC=5, TA = 50, CYA=25
8. added 1 gallon chlorine 10%
9. 5/8: readings : FC = 26, TA = 80, CYA = 25
10. 5/9 readings: FC = 19.5, TA = 80, CYA =35
11. 5/11 readings: FC = 6.5, CYA = 45

Should I be surprised at these high FC readings?
But...when I use my small Taylor test kit to test chlorine & PH, I get significantly different readings.
Like today, 5/11, using my Taylor kit, chlorine = 1 (very light yellow) but why did my TF-100 chlorine drop show 6.5?
My "chlorine only" cylinder in my TF-100 has a black crusty, film sticking to its sides so I wonder if that has something to do with it.
It's not the first time readings between my TF-100 vs. Taylor (small blue box) were so different.

Thanks for your help,
Chuck.

 

[ajw22]

The OTO chlorine test in the Taylor K-1000 is good only for telling you if you have chlorine or not.

I suggest you clean out your testing cylinders.

Water Testing Errors - Further Reading

www.troublefreepool.com

BTW, Your CYA is 30, 40, or 50. We round up and if the dot disappears between 40 and 30 we round up and call it 40.