Better Test for CYA?

Jersey Devil

Platinum Supporter
Aug 4, 2007
Jackson, NJ
BBB working great so far after Spring Baquacil conversion but I am a little concerned about getting accurate CYA readings. The test is so critical to proper treatment yet it is so subjective. Today I did my normal Saturday am readings and got an initial result of between 50-60. Last week I was at 40, which was exactly what I have been running. No added CYA and only a little evaporation so I was concerned with the big jump. I rinsed, resampled and re-tested, this time being very careful to hold the cylinder exactly waste level and in proper daylight. Result = 40 ppm. I am 5'6" tall with relatively poor vision (yes, I had my glasses on!). If I were 6'5" with eagle eyes, I expect that I might get a different reading. I will order the 50 ppm standard solution to "calibrate" my eyes.

My question: Is there a sophisticated lab test (e.g., turbidity meter, nephlometer, etc) to accurately measure CYA? If so, what is the relationship between the reading and CYA level?

What do the pool stores use and which national outlet actually does this test? I realize it is difficult to trust the "kids" running the tests in the stores, but if I knew the technology I might be able to access it at one of the labs where I work. (And besides, I am just curious - This is Chemistry 201, right?).

In the interest of complete disclosure my morning readings are:

FC 4.5
CC 0
pH 7.6
TA 90
CYA 40
CH 70


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
There is a several hundred dollar specialty tester that is better than the usual CYA test at low levels, about the same at more reasonable levels. Other than that, the standard test is the best you are going to get. Pool stores are routinely way way off on the CYA test.

You can learn to do the test reliably with practice.

Jersey Devil

Platinum Supporter
Aug 4, 2007
Jackson, NJ
If anyone knows what the test principle of the specialty tester is I would be interested. As I said, I have access to some sophisticated labs, but mostly I'm just interested. A web link might be helpful.


LifeTime Supporter
Jul 11, 2010
England, UK
We test CYA with a photometer and it seems to give pretty good readings - we were concerned about our testing procedure so got some had different people to carry out the test. The FC results were pretty variable, but the CYA results were in good agreement. Our kit is the old version of the Lovibond PC Checkit 3 in 1 Cl pH Cys, and I think it measures CYA up to 200. I'm sure there must be equivalent kit in the US.

another one

Well-known member
Jul 1, 2010
Seattle area, WA
You can get a 50ppm standard solution so you can see what the end point should really look like.
Can you dillute the standard solution with 50% distilled water to measure 25? I'm trying to get my CYA down to 20 to 25 and my readings are bouncing rather than lowering as I slowly replace water - but I'm also raising the temperature of my pool from 64 (last week) to 80 (today). I warmed up the cooler samples by placing it in a bowl of hot water to get it above 70 degrees.