Testing for CYA - different results for different methods

Water_man · Jun 23, 2011

Hi all,

I'm in the process of opening my pool, although the current weather indicates that the swimming pool season wouldn't start until mid July :rant:

Obviously, the first two values we check are pH and CYA.
The pH was high so I lowered it to 7.2.

For CYA I used the Taylor kit and the TF Test Kits. I like the TFT for CYA because it can measure lower values up to 20 while the Taylor stops at 40. Both kits were about 2-3 years old and during the off season they were kept in the fridge.
Here are the results:
two different dip strips - close to zero.
pool supply store: 9
TFT: 40
Taylor - at 40 I could still see the black dot.
It's hard to believe that four are wrong and only one is right.
So I went with 9 ppm.

I just wonder what happened to the reagent of the TFT Kit.

Crzyfrlss1 · Jun 23, 2011

Re: Testing for CYA - different results for different method

I'm just wondering if it's really feasible to keep a test kit in the fridge?

rcy · Jun 23, 2011

Re: Testing for CYA - different results for different method

Doesn't Taylor recommend yearly replacements for reagents?

Water_man · Jun 23, 2011

Re: Testing for CYA - different results for different method

rcy said:
Doesn't Taylor recommend yearly replacements for reagents?

Certainly. What's wrong with having more sales? Most chemical reagents are stable , especialy in low temp.

chem geek · Jun 23, 2011

Re: Testing for CYA - different results for different method

Water_man said:
I like the TFT for CYA because it can measure lower values up to 20 while the Taylor stops at 40.
:
TFT: 40
Taylor - at 40 I could still see the black dot.
:

The Taylor kit should go down to 30 ppm, not 40 ppm (see top of vial in the photo at the bottom of this link). Was the water even cloudy when using the Taylor reagent? I have both the TF-100 and K-2006 kits and have always found them to be consistent.

Water_man · Jun 23, 2011

Re: Testing for CYA - different results for different method

chem geek said:
The Taylor kit should go down to 30 ppm, not 40 ppm (see top of vial in the photo at the bottom of this link). Was the water even cloudy when using the Taylor reagent?

You're right. I didn't read the number well - I thought that all the way to the top was forty. The water was indeed cloudy

cillovely · Jun 24, 2011

Re: Testing for CYA - different results for different method

Water_man said:
I'm in the process of opening my pool, although the current weather indicates that the swimming pool season wouldn't start until mid July

I hear you on that!! Just got mine all converted over from Baqa-poo to the BBB method and it's been mostly lousy days since. I was lucky enough to be home early this week and got two days in.

Let's hope for some improvement up here in MA!

frogabog · Jun 26, 2011

Re: Testing for CYA - different results for different method

The CYA reagent I'm using is from an out of business company called Master Tech (I think) which is a full old school color comparitor kit that tests to 10ppm FC and TC. Dad handed me down this massive kit so I may as well use up what still works, right? There are two full bottles of the CYA reagent (it's like a goldmine... they are 2oz bottles), which have to be at least 10, if not 15 years old and if they work, I figure I'll use them up and buy more later.

So I got a new HTH 6-way kit, and compared. Same result. Spa/pool store guy said it should be fine when I inquired (shrugged it off as if it doesn't really expire). I don't know how much he knows for sure but he didn't try to sell me new CYA reagent, so he gets a point for that.

It seems to work fine and I know it's ancient. YMMV of course. I can guarantee it was not stored properly, however our climate is fairly mild (if you don't consider rain an extreme weather condition).

I'd go with the taylor and TFT numbers and call it 40-45, 9 seems kinda low. How much water did you replace since closing last year? What was CYA then? Check the calculator but I bet it won't change minimum and target if it's 40 or 45 and if you dose to get from 9 to 40 and you're really at 40, then you'll be at 70.

Happened to me this year. Overdose... (only by 10ppm tho). I didn't loose as much as I thought by draining for winter and the gallons of rain that fell. Those dip strips never register CYA unless it's 40 or above anyway. I only saw the slightest change after the overdose on the dip strip test (40ppm). I didn't trust the old CYA yet and used a couple dips when I opened the pool. They fooled me into thinking it was 10 or less because it was soooooo light. I then added 20ppm CYA and overshot it by 10ppm.

The weather here sucks too. 20-30 CYA works for us, we lack all that sun everyone else has to deal with. Maybe when the kids get back from camp in a week the sun will be out. The forecast is... bleak.