I have two different CYA test kits -- one is the Taylor test that comes with the K-2006 (the small tube), while the other is a Blue Devil kit -- the larger tube with the "slider" that is sold by various companies, including Taylor. Both kits are recommended by various people.
I'm finding that the two kits are constantly giving me what I would call substantially different results. The Taylor kit gives me around 90 ppm CYA, while the "slider" kit shows much lower levels -- more like around 60 or so. I'm being VERY careful to follow all instructions, and to accurately use the correct amounts of water and reagent. I get consistent results on each kit -- i.e. successive tests show me the same results -- but the kits disagree by about 30ppm.
What could be causing this? Which kit should I trust?
Note that I ordered the Taylor K-1720 kit, which seems to be a larger and easier to read version of the CYA kit in the K-2006. I'm hoping that this will be a tie-breaker, but I won't have it for a little while still, so I won't be able to post the results for a bit.
Thanks for any feedback on this,