FWIW - Blue Devil vs. Taylor CYA tests wildly different (again)


Bronze Supporter
Oct 2, 2016
albany, ga
Just posting in case it may help someone else. I'd asked a while back about why the two tests would come out so differently. Never really got an answer, so I just stuck with the blue devil method because I thought it was easier to read. I could tell things weren't really right based on the appearance of the water even though all the tests should have been in TFP 'perfect' range. It was driving me crazy and I had a suspicion that my CYA was off because I had started going solely on results from the Blue Devil CYA tests. I tested and retested with the BD unit and it was consistent. 70, right where it should be after my addition. I couldn't shake the feeling something wasn't right. I broke down and purchased more Taylor 0013 reagent and it tested off the charts. Dilution test showed it was 120. Still have no idea as to why, but the numbers, run repeatedly, don't lie and it now makes sense that what I was seeing was most likely the beginning of an algae outbreak (even with High Chlorine and good CC numbers). Maybe just bad batch of Blue Devil reagent..., no clue. If anyone would care to speculate, I'd love to hear it. I'll stay with the Taylor method from here on out because I can no longer trust the Blue Devil method/solution...


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

I have no idea what happened in your case, but I have been using the Blue Devil CYA test for a couple of years with no issues...

I actually went around my neighborhood and got several samples of pool water.. I had about 10 samples.. I can say they were all different, some low most very high.

My point is that my tests do not duplicate the problem you had.. My high tests were well above 70.. and were each a little different..

Something is just not right on your end, but I have no idea what.. :(


Jim R.
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