Chlorine vs Bromine in test question

[FatherOHenry]

Greetings!

I've recently replaced my sister's pool guy and so far things have been going swimmingly well.
I've been using a K-2006 kit I bought before I learned of TFP.

On March 4 I removed the last of the pucks the pool guy had been using and did not add anything else.
By March 9 the K-2006 was reading Cl at 2.2ppm. At that point I added liquid chlorine to bring it back up to 4ppm.

Today I decided to compare it against results from a K-1004 kit she had in the garage.
The K-2006 gave me a chlorine reading of 3.6.
I'm unsure how to read the K-1004:



if I'm looking at Cl it appears to read maybe 1.6.
if I'm looking at Br it appears closer to 3.5.

I assume using liquid chlorine I should be reading the Cl numbers.
Could the K-1004 reagents just be bad?
What am I missing, misunderstanding or doing wrong?

Thanks!

 

[Oly]

Yes you are correct you are testing for Cl, use that scale.
If you want to compare test kits and reagents test the same water at the same time. But determining which is correct will require a standard solution with a known ppm Cl.
The color matching tests have limitations and one is the precision. You want a FAS-DPD drop test (titration) to determine ppm Cl to 0.5ppm using 10ml of pool water.

Good info here..... Test Kits Compared - Trouble Free Pool

Extended Test Kit Directions Archives

www.troublefreepool.com

 

[YippeeSkippy]

If she's not got a bromine pool (and I hope not! ugh!) you only need to concern yourself with the CL side of it.

Most of us don't use that color matching block for more than just a confirmation that "yeah, there is *some* chlorine in there" but without assurance of exactly how much. Most of use use the FAS-DPD test as we want to know not only an exact FC (free chlorine) number, but also the CCs (Combined Chloramines, aka the "cooties"). That's what the FAS-DPD tester tells us.

Maddie