CYA newbie mistake

Puppiesonacid

Well-known member
May 11, 2016
195
MD
#1
Wish the laminated card would say use room temp water for the test, instead of just on the extended directions on this forum. Since it seems to be a major thing.

Pool is perfect... beyond perfect other than CYA... I thought it was 10, added some to bring it up... read the directions on here, and realized i did it wrong, so got some room temp water, and now the CYA is at 70.

Guessing it was 50 and not 10 before. Cold water is bad :)

Learn from my mistake! I have
 

domct203

Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
3,959
CT
#2
How cold is the water, and how much CYA did you add? Are you performing the test outdoors on a bright sunny day with your back to the sun?

A 40ppm swing from cold to room temperature water seems very excessive.
 
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Puppiesonacid

Well-known member
May 11, 2016
195
MD
#3
Ok. so last year it was around 100 CYA. pool store and me not knowing anything got it up that high.

So 50 is probably correct as I drained half the pool for winter and let it fill up.

Water was 59 degrees so not freezing when I first tested it, and the tube filled up and was just slightly cloudy, so i figured 10.

i added about 20 ppm of cya... so i tested again with the 72 inside temp water and it came out to 70 cya.

So by all calculations that is correct.

Just weird that it showed 10 cya at 60 degrees...
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
#4
We always say that anything less than 30 gets to a point where it is really too difficult to accurately measure. As you know, cold water temps can effect the results, and so does incandescent lighting which is why outdoor (bright) sunlight is so important. Also remember there is about a +/- 15ppm swing in that test due to various conditions, so it's the trickiest to perform.

Nevertheless, if you're confident of that CYA of 70, all is not lost. Simply adjust your FC accordingly as noted on the Chlorine/CYA Chart and you'll be fine. Over the course of the swimming season, I suspect it will drop a little from standard consumption, splashout, backwashes, etc. You'll be fine as long as you stay close to that chart. :)
 
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Puppiesonacid

Well-known member
May 11, 2016
195
MD
#6
PS. The first test was outdoors with bright sun, and the tube filled all the way up, just slightly cloudy could see all the way to the bottom. the next one was indoors with room temp water, but the dot disappeared between 80 and 60... kind of right at 70. using indoor lights and some outdoor through the window. looked the same in both types, and tried it 2 times with same results... so... yea... Meant to test it again yesterday outside, but now I got 2 more days of rain coming.
 

JamesW

TFP Expert
Mar 2, 2011
13,049
#7
CYA should test correctly at 60F. At 40 F, it might test slightly higher, not lower than actual. Did you wait the full time for the sample to develop?

Do pool or spa water samples have to be at "room temperature" before testing begins?
With one exception, no. Our lab has run the pH, total alkalinity, calcium hardness, free chlorine, and cyanuric acid tests on known standard solutions at approximately 104°F, 75°F, 60°F, and 40°F. Only at 40°F did the CYA standard solution test higher than its actual value (after accounting for test variability). All other tests were unaffected by temperature differences.
https://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=86
 

slickraft

Well-known member
Oct 7, 2016
219
Phoenix
#8
When I ordered replacement chemicals this spring from TFTestkits.net I also got the CYA standard test solution for $5 and after practicing with it, I now know that I am doing my own tests correctly. The CYA test is the one that I always wondered if I was close or not since it can be very subjective. Now I know that for my eyes, it takes full bright direct sunlight at waist level to read correctly.

TFTestkits.net
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
9,218
Evans, Georgia
#9
When I ordered replacement chemicals this spring from TFTestkits.net I also got the CYA standard test solution for $5 and after practicing with it, I now know that I am doing my own tests correctly. The CYA test is the one that I always wondered if I was close or not since it can be very subjective. Now I know that for my eyes, it takes full bright direct sunlight at waist level to read correctly.

TFTestkits.net
Good point, slickraft. I found it helpful when I was new also.

Yip :flower:
 
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Puppiesonacid

Well-known member
May 11, 2016
195
MD
#10
Thought to post this earlier, but forgot. I think I get what was wrong now. I tested it thinking the rain water just mixed with the old water without ever running the pump after winter, and when i opened it. So I guess the new water sat on top of the old so it was 10, then it mixed, and turned to 70 after me adding 20ppm cya.

Cold water didn't affect it after all after reading some other things as well as what is on this thread.

So the mistake is mix the water before doing any tests :)
 

Serious1

Silver Supporter
Jul 13, 2016
101
NE
#12
When I added stabilizer it took at least a day to get an accurate, consistent reading. That's with the pump running 24/7 so I always cringe when people say to test CYA the same day they added it. It's better to wait overnight or a couple of days and get that one right IMHO.