CYA test is pretty subjective, isn't it?

[waterbear]

The alternative is to use a turbidity meter or colorimeter. some pool stores use them. some use the melamine reagent and the disappering dot. Meters are expensive (good ones in the range of about $600 and up) and do need to be calibarated. If the test is done properly it can be as accurate as a meter (almost). Where I work uses the LaMotte Waterlink Express meter to test (it uses little plastic tubes with a measured amount of reagent in them [Unit Dose Vials] and 3 ml of water is added for the test. They are thrown away, tube and all after each individual test. The meter is calibrated with a blank before each battery of tests) and I get identical results at home with :
1 Ben's ps234s
2 Taylor K-2005
3 Walmart Aqauchem 'cheapie' kit
(as a side note test strips always give me a lower reading)

Another pool store in town uses Taylor's water lab and the cya results depend on who is doing the test. When the owner does it it matches. when the young girl does it it is ususally low (prime example of bad testing procedure, i guess)

The way I do the test at home is as follows:
The first test I do is CYA and I read it about 3-5 minutes after I do it. I start doing other testing in the meantime, usually my FC, TC and maybe pH.
the procedure I use is:
1. make sure the pool water sample is at room temperature (70-80 deg.) before I start because cold temps will slow down the reaction and can give you a low reading because of incomplete precipitation and I have read that high temps (above 80 deg.) can also have adverse effects on the reading (don't exactly know what but possibly allowing some of the precipitate to dissolve and also give a low reading) and then mix pool water sample and reagent in bottle and shake for 30 seconds.
2. let bottle sit for a few minutes and continue with other water testing.
3. make sure I read CYA test before 5 minutes from time of shaking has elapsed. (don't know how important this is but I have read that the test should be completed within 3-5 minutes from different sources)
4. before transferring to CYA tube shake bottle hard for 10-20 seconds.
5 .VERY SLOWLY (almost a drop at a time) transfer solution to tube either with northern window light or outside in shade. Tube is at waist level.
6. read results when black dot seems to completely dissappear.
7. If I want to check my results I pour solution out of tube back into mixing bottle and repeat test. (this is a good way to learn if you are having trouble reading it.
8. wash tube and bottle out carefully and completely so no residue is left in tube

I am the first to admit that I am anal about my water testing! but if you are having problems then perhaps you might want to try something similar to this.