CYA 50ppm Standard results

[TimS]

Please check me on this. I bought the CYA 50ppm Standard solution from TFTestKits to verify my testing procedures. The way I understand it, I use this solution in place of pool water, mixed 50-50 with the CYA reagent, (just as I would with pool water.) Mix it up, and let is sit for 30 seconds. Mix again, and pour into the view tube. In direct sunlight, with my back to the sun and the view tube held at waist level, I should get a reading of 50, correct?

The reason I ask is that to my eye, the dot disappears at 70, instead of at 50. The way I've been reading my test, my CYA must be 20ppm lower than I thought it was. I started the season with a CYA of 40 (by my reading) which I thought was extremely low since my reading last winter was 70, and I only replaced about 15-20% of the water. I later added enough CYA that I should have reached 80, but it never got there. I have been operating under the assumption that my CYA is 70, but based on this test, it must be closer to 50 or 55.

Note that if I do it the same way, but facing the sun, I get a reading of 60 instead of 70, but still not 50.

Anyone have any guidance or advice on why this seems to read high to me?

Thanks,
Tim.

[Edited because I had written "50%" instead of "50ppm" - It's only a factor of 10,000! ]

 

[JasonLion]

Re: CYA 50% Standard results

Right, you do the test with the standard solution just as you would do it with pool water and the final result should be a test result of 50.

I find that when I am getting close to having added enough liquid to the view tube the black dot will disappear completely for a moment, and then as I stare at it, it will reappear. That means you are getting very close but are not quite there yet. The black dot should completely disappear, so there isn't even a hint of it having ever been there, even when you stare directly at it for several seconds.

Remember that you can fill the view tube over and over for several minutes after mixing the test solution, pouring it back into the mixing bottle each time. That gives you a chance to practice what it should look like several times and get a feel for what it looks like at 50 vs what it looks like when you stop the way you have in the past.

 

[TimS]

Thanks, Jason. I thought I was following the directions properly, I just wanted to make sure. Guess I'll have to keep working at it.

 

[duraleigh]

Hey, Tim,

The CYA test will always be the most subjective testing you do.

Many people who first test are puzzled when the test returns a result of zero CYA. We probably should do a better job of explaining that it is not "naturally" occuring and zero is a common value.

I do notice that after a few tests, folks pick up on it right away and there are seldom any "continuing to have problems" posts. Practice seems to be the key but, most of us agree it is the test that is the most difficult at first.

 

[mynewpool]

I agree it is the hardest test to do. I still have problems to this day. I just try to do it about five times back to back.

 

[anonapersona]

I keep adding solution until there is no dot, nor is there a square or an oval... asking myself all those questions seems to clarify when "gone" is "gone".

 

[jt100]

Tim, I'm with you. I always seem to come up with 60 with the standard. It gets to the point that i'm saying to myself "I think i can see the dot, or maybe not, or maybe there it is....hmmm...." With my own pool, i round up high just to be on the safe side. I'm still pretty new at it though

 

[TimS]

Maybe I'm suffering from "Phantom Dot Syndrome." I'm never entirely sure where it really disappears. There have been times I've done the test several times back-to-back and come up with numbers that vary as much as 30ppm. It's rare for it to be that high, but it does occasionally happen. Usually where my problem arises is at that point where there's just the slightest hint of a dot - is it really there, or am I seeing things? Typically, if I stare at it long enough, I'll see the dot again, even when I'm sure it's not really there anymore.

Granted, being off by 10ppm CYA in the normal course of things isn't going to hurt much. I too round up to be on the safe side, and at worst, it uses a bit more bleach. In my pool, this amounts to about an extra 1 1/2 gallons per week.

I think I'll start the "Phantom Dot Syndrome Suffers Mutual Assistance Group" (PDSSMAG) Our goal will be to take our best guess at when the dot disappears, then to drink beer (or other libation of choice) until:
1) We are sure that we can't see the dot in the bottom of the tube
2) We are sure that we can't see the dot in the bottom of either tube
3) We can't see the tube or the mixing bottle
4) We just don't really care anymore and have to go to the bathroom
whichever comes first.

We'll have a 12 step program where no one will be seated more than 12 steps from a cooler or refrigerator.

There will be no membership dues, but everyone will need to provide their own testing supplies (including libations.) Anyone interested?

 

[TimS]

OK, after repeated testing both with the 50ppm Standard and with my pool water. I've discovered the following:

1) My hand shakes. (This is not a new discovery!) This makes reading the test incredibly difficult and inaccurate, since the solution is never at rest and the surface still.
2) Holding the view tube directly in front of me at waist level, and looking straight down into it reflects my head, which reflection looks an awful lot like a fading black dot.
3) For me, I can get the same reading inside under incandescent light with the tube sitting on a white piece of paper as I can holding the tube in direct sunlight with my back to the sun.
4) My CYA is much lower than I thought it was.

To solve #1, I attached an alligator clip on a fine jumper wire to the rim of the tube, and hold the wire instead of the tube. This isolates the vibration of my hand enough that the solution in the tube is not disturbed, the surface is calm, and I can read it with much more accuracy.

To solve #2, I don't hold the tube in front of my navel, but off to the side a bit. I can still see down into the tube just fine, but I can't see my own reflection.

On #3, there's nothing to solve, just an observation.

#4 is interesting. This error has actually compounded over time. Last year, I thought I had closed with a CYA of 70. When I opened this spring, my CYA was 40, but I didn't replace enough water to account for this. After burning through more chlorine than I thought I should be using, I added CYA, and thought I had reached 70ppm. What I've discovered is that my CYA is actually 50 instead of 70. Every CYA reading I've ever taken appears to have been wrong.

Now I need to do some further testing to see if my bleach use makes more sense working with a lower CYA number.