CYA Test

[TomTinNC]

At the beginning of the year, my CYA was off the charts, and my pool was a swamp. Combined with the de-swamping process I replaced some of the water (about 50%) to get the CYA numbers down. I had pucked my pool for the last 3 years, prior to finding this site.

Current Numbers:
FC:9
CC:0
TC:9
pH:7.4
TA:70
CYA: 60-80? (hence this post)
CH: 890...yep, I know its a nightmare. Gotta love Cal-Hypo and fill water loaded with Calcium.

When I did the partial drain and refill, and got my TF-100, my CYA tested at 50. I have not used any pucks or "shock", or anything else that contains stabilizer in the pool. The other day, a particularly sunny day, I tested my CYA again and it tested at 90 or so. I thought that was a way high, and it was unexpected. I poured the reagent back in the squirt tube, and began again to slowly put reagent back into the view tube. Came up with 80.

Today, when I tested again, it is slightly overcast, I came up with 70. I have run this test over and over again, out of reagent now, and have to order some more. I put my back to the sun, put the view tube down at my waist, and I add the reagent until the black dot dissapears. I'm assuming that my CYA is somewhere between 60-80.......eliminating my extreme results.

I do follow the mixing directions once I add the reagent to the water in the squeeze tube. Mix thoroughly for 30 seconds. Set down for 30 seconds, mix again, then test. Back to the sun, view tube at my waist line.....

I wear glasses, and get a lot of glare in my vision when doing this test. I get lower results on slightly overcast days when I'm not dealing with the glare. I am also 6'4" tall. I have no idea what my exact CYA level is. I'm not that worried about it, I'm maintaining maximum FCs right now (9) and my water looks great.

Any suggestions or help would be great. What time of day do you all perform the CYA view tube test? Overcast? Slightly overcast? Full sun? Should I lift the tube a bit?

I have company coming in a week, and I do plan on doing another drain and refill to get that CYA below 50, but I don't want to harm my pool which is currently spotless. I'm not consuming a whole lot of chlorine...bout a gallon and a half a week...sometimes less depending on the weather. I'm kind of happy with the current condition of the pool, and somewhat reluctant to change anything right now.

Tom

 

[linen]

The cya test is difficult and does require good lighting. Bright sun, to your back while holding tube at waist. Have you looked at the extended directions: http://www.troublefreepool.com/extended-test-kit-directions-t25081.html#p206397

Another thing you can try is the a reference solution...I think Dave sells them with a value at about 50 ppm at tftestkits.

 

[Richard320]

Order the standard solution from TFtestkits.net when you order CYA reagent. Then you can experiment to see what you need to do to get the right reading, then your test will be accurate. Might as well check inventory on the other reagents and save on shipping. I imagine you use up a lot of R-0012 with that CH reading! Try using the instructions for a 10 ml sample- do you really care if you get 875 or 900 instead of 890? Close enough! If you don't already own a speedstir, get one of those, too. Makes the CH test a lot easier.

 

[TomTinNC]

I have a speedstir. I'll try the smaller sample instructions, I just found that for the CH. I know its bad, its not going down. My fill water is major culprit....3 years of cal hypo would be the other culprit. I'll try and order that standard, I need the chlorine drop test reagents anyway. Thanks.

 

[gboulton]

I wear glasses, and get a lot of glare in my vision when doing this test. I get lower results on slightly overcast days when I'm not dealing with the glare. I am also 6'4" tall. I have no idea what my exact CYA level is. I'm not that worried about it, I'm maintaining maximum FCs right now (9) and my water looks great.

Tom,

We're in almost the same boat! I too, wear glasses (trifocals as of last month...man I'm getting old) and am 6'6", so the light takes a few seconds make it from my waist to my eyeballs. :lol:

Your varying results on cloudier or sunny days actually does have an explanation, and it's a fair bit simpler than you think. You get lower results on cloudy days for the same reason photographers prefer to shoot portraits on cloudy days...shadows.

Over simplified a good bit :

1) Lower CYA = MORE solution in the tube.
2) Water cloudiness...even in our CYA tube...is the result of particles in the water.

Those particles create shadows...and thus darkness...as light passes through the solution. Brighter light? Darker shadows.

A cloudy day offers diffuse, or "scattered" light, which "softens" shadows, resulting in a solution that's a bit easier to see through....thus you can put more of it in (resulting in a lower CYA reading) on cloudier days.

There's a whole bunch more fancy wharrgarbl about contrast, and further diffusion of light by the solution, and so on and so forth...but that's the basic premise.

Personally, my CYA readings seem to be about 10% lower on cloudy days, as a rough estimate.