CYA testing - "just disappears" seems subjective

[Pauls234]

As I am sure is common, my test kit (Taylor k2006) has me pour the mix of water and regent until the black dot "just disappears." The first time I tested I had a reading of 40. Today, since I've been using trichlor pucks, I decided to test again to ensure I didn't blow over 50 before I transition to the BBB method.

I got a reading under 30. From reading this forum I know that doesn't make any sense given there was no water replacement. So, I must have had a different idea of what "just disappears" last week, than what I think it means today.

What does "just disappears" really mean? If the dot becomes pretty hard to see but still discernible if I squint or focus or close one eye does that count? Or should it be pretty much impossible to see if I look really really hard?

Maybe I am splitting hairs but reading about what seem to be common and almost structural problems with high CYA has got me nervous.

 

[JamesW]

http://www.taylortechnologies.com/chemi ... ntentid=44

Also, see this page for video demonstrations of each test. Choose the test you want to see demonstrated.

http://www.taylortechnologies.com/produ ... ber=K-2006

 

[Richard320]

Lighting plays a huge part in the test results. It needs to be bright out, but without any direct sunlight giving you glare off the top where you're looking. tftestkits.net sells a standard 50ppm solution you can use to check yourself.

 

[anonapersona]

Sunlight is way, way brighter than indoor lighting, so in sun the white is whiter and the dot is gone a bit earlier. Be certain that your lighting conditions are the same before you worry about sudden changes. And, no sunglasses, please.

 

[MattM]

It is very easy to make mistakes on both the CYA and CH tests - the others are piece of cake. CYA and CH are OK too but it takes longer to get a feel for how to do it exactly right. CYA depends on excellent lighting, mixing properly, and having exactly equal amounts of pool water and R013 in the testing vial. The first few times I did the test, it was easy to get results 20+ pts different from each other. Now it is more like a 10 pt range and if I know what number I expect to get, I can treat it as that number +- 5. It just takes practice and being careful/slow.

 

[257WbyMag]

I always make sure that I check CYA at the same time of day. That seems to counter some of the variances with ambient lighting that can affect interpretation.

 

[8corneflakes]

I agree, it is very subjective. I doubt myself every time I do the test. Often, I walk around the house asking people, "can you see a black dot in here"? Only when someone asks, "what black dot?", am I satisfied.

 

[aa62579]

Sun to your back, hold the vial at waist level. Remember that you can pour the mixture back into the squirt bottle and repeat the test several times. I will do it once or twice the normal way (add drops until the dot disappears) and then I use another method to check myself. If I had come up with 50 as my CYA, I would redo the test, but this time not watch the dot. I would just look at the vial and add the mix to the 60 level. I then hold it waist high and confirm that I can still see the dot. I then bring the mix back up and add more mix until it gets to the 40 CYA level. I take another look at waist high to confirm that this time I cannot see the dot. Sometimes I repeat this, getting closer to my level (so I would look at 55 and 45). This confirms to me that my result is in my comfort window with is +/- 10. Also, but not watching the dot the entire time, I have removed the ability of my mind to play tricks on me and still see something that isn't there.

 

[anonapersona]

I also do what aa62579 said. I do it once the normal way, watching as I add to the test vial, then pour everything back and fill to each line on the test vial ( 20, 30, 40, etc) and take a look.

Remember that it is about seeing the dot, not seeing the larger paper that the dot is on. Go look at the picture above to see what I mean.

 

[Pauls234]

Thanks for the input. The pictures from taylor's site are pretty helpful. I still see a bit of the black dot in the end test pic, but now I have a better feel for what "just disappears" means to the test creators.

 

[cody21]

+1 - I've been having the same issues with the test ... Given that the value for CYA is so intertwined with the value we are shooting for with the CL, it's too bad this test isn't a bit less subjective - IMHO .. Hopefully more experieince will solve this for us newbies.

 

[frogabog]

In the Taylor images, the end point yes you can see something but it's not the black dot. It's the bottom of the tube. If you look closely, the black dot is smaller than the bottom of the tube (diameter wise) and the dot is clearly not visible.

 

[Leebo]

Look at this test like this. We use this test to figure out your FC level. With a CYA level of 30 you want your FC between 2-6ppm. With a CYA level of 50 you want to stay between 4-8ppm. There's really not a huge difference between the "goals". Even with a huge margine of error on the CYA test, if you keep the FC between 4-6 you're 100% safe.

 

[UnderWaterVanya]

In the Taylor images, the end point yes you can see something but it's not the black dot. It's the bottom of the tube. If you look closely, the black dot is smaller than the bottom of the tube (diameter wise) and the dot is clearly not visible.

Our monitors are not calibrated and neither are our eyes so we may not be seeing exactly the same things. I see what he sees - I see a black dot - the right size - faintly within the bottom of the tube. I don't know what I would see in person on that test - but the picture shows me a little of the black dot when viewed on my computer - not sure if my phone gives the same impression or not.

 

[frogabog]

I see a darker circle at the bottom of the test tube, but not a smaller one inside it. I'm on a new i-7 DV7 laptop at the moment, but I've used as many as 3 other monitors/machines in the past to view that image and I always see the same thing. If you can see the dot, you should be able to see both the inner dot circle as well as the outer circle that is the floor of the test tube. Is that what you're seeing? Two circles down there?

Regardless, the dot should not be visible at your end result. By the time you have to start squinting really hard or using one eye, tilting your head or shifting position to the sun to see the faintest hint of the dot... the dot should be considered gone.

 

[UnderWaterVanya]

I see a darker circle at the bottom of the test tube, but not a smaller one inside it. I'm on a new i-7 DV7 laptop at the moment, but I've used as many as 3 other monitors/machines in the past to view that image and I always see the same thing. If you can see the dot, you should be able to see both the inner dot circle as well as the outer circle that is the floor of the test tube. Is that what you're seeing? Two circles down there?

Yes. One is easier to see (the outer one). The inner one is very faint and barely visible.

Regardless, the dot should not be visible at your end result. By the time you have to start squinting really hard or using one eye, tilting your head or shifting position to the sun to see the faintest hint of the dot... the dot should be considered gone.

My own testing is tough - I have poor vision (Yes I get the irony) and at the distance for the recommended test I sometimes have to EDIT (LOL - it doesn't like my innocent use of a term that has been coopted for other meanings) shift my head sideways and look a few times at it before I know what's up. I wish they made a version calibrated for side lighting and holding it closer to the face. Then with a calibrated light source we could just go to town!

LOL
Wishes are easy.

 

[frogabog]

I need new glasses... this getting old stuff is for the birds! My eyes are so much worse than ever, I can't even read texts on my phone without them now.

I did a little squinting, and moving of my monitor and head, tilting, and some wishing... I think I can see what you're seeing. The faintest hint of the inner dot. I think the key is that by the time you're squinting and employing super x-ray vision it's time to call it gone. As Leebo said... the range for a change in FC targets is wide enough that you should be ok, regardless.

 

[JamesW]

You also want to make sure that the test vial and black dot are clean. If there is any residue obscuring the black dot, then that will throw off the accuracy of the test.

 

[ajones02]

is there a specific amount of R013 or pool water that goes the mixing bottle for this test? BTW, i have the TF100...........

I've never poured the R013 into the bottle and then measured it nor have i done that with the pool water either. Just thought it would be better to use a tube to get equal amounts of the mixture.

 

[linen]

Just like looking to long and hard at the vial when doing the testing, also applies to looking at the screen image. Look long enough, and you can convince yourself into seeing anything. When I glance at the screen image, I do not see the "inner" dot. When I stare for a few seconds, I think I see it.