Testing CYA in correct light

[Jackie G]

Is anyone able to give advice on how to test for CYA consistently and accurately please?

I tested my CYA level a couple of weeks ago, and again a few days ago and it was showing as just below 30. I tested it with my back to the sun (it was a little cloudy with the sun peeking through) and held the tube at waist level. I did this numerous times as I was surprised the CYA level had dropped so much from 60, which it had held steady at since April.

Prior to this, my CYA had held steady at 60 since April. I was confused that it had reduced so much to less than 30 as we hadn't filled the pool up to dilute it, and I had thought you didn't lose CYA unless it is diluted in some way (significant rainfall or draining and refill).

I tested my CYA this morning again this morning and it was 40. I tested by standing with my back to the direct sunlight and holding the tube at waist level. So still less than the 60 it had held steady at for so long. We did top up the pool yesterday but I still don't think this would have explained the drop from 60 to 40.

This got me thinking about optimum conditions for testing CYA, and how I can ensure my tests for CYA are accurate.

We don't have full sunshine (probably most of the year!) and so how can I ensure my tests are consistent if I can't have the same sunshine conditions?

I'm slamming at moment, and it's taken just over 2 weeks already, but I was working on a target slam level of 12 instead of 16 based on my CYA level of less than 30! No wonder we weren't getting anywhere much, although last night FC only dropped 1.5

Anyone give advice on how best to do this test so that I can be sure my FC levels are as they should be? The more I try to make sense of my readings, the more confused I am getting

 

[Texas Splash]

Well, two things could've happened in your scenario. One, there have been reports of some brands of stabilizer simply degrading quickly. Not sure if it is an occasional bad batch from the manufactures or what, but I had that happen to me a couple seasons ago. I had to buy a different brand and it helped much better. The other problem is lighting. You said you tested this morning already, but at that time (so early) the sun would not be high enough for a good reading. I'd recommend testing sometime between 11:00 am and 4:00 PM when you have a good amount of high sun - assuming it's a sunny day of course. Too early or too late and the low angle of the sun won't give you the brightness needed. Then the dot will probably disappear quicker giving you a false (low) CYA reading.

CYA Testing:
Proper lighting is critical for the CYA test, so you want to test for CYA outside on a bright sunny day. Taylor recommends standing outside with your back to the sun and the view tube in the shade of your body. Use the mixing bottle to combine/gently mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then gently mix again. Then, while holding the skinny tube with the black dot at waist level, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. If it helps, pour a little, look away, then look back and pour some more. Once it disappears, record the CYA reading. After the first test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate the CYA reading. If you are still questioning your own results, have a friend or two do the same test 2-3 times. Share your results only after everyone is done to see if you came up with the same average results.

 

[tomfrh]

You don’t need identical lighting each time. You just need even diffuse light. I think this is the idea of back to the sun.

tempetature can make a big difference to results. It needs to be warm enough for the reaction to work.

 

[Jackie G]

Ok thanks so far

When I originally was testing back in April it was a lot cooler. It's now very warm. Would that make a difference do you think? I think it would have been around 65 - 70 Farenheit

It's now more like 80 - 90 (yes, we're enjoying some hot weather in the UK!)

What happens if it is a cloudy day, period? Any suggestions as to what will be best?

 

[Texas Splash]

If the water is chilly, say below 60, it can skew the results, so we recommend bringing the sample indoor for a few minutes to worm up before going back outside. If it's cloudy, you'll lose some effectiveness of natural lighting, so it's best to wait until the clouds clear.

 

[Jackie G]

OK thank you everyone. I'm going to take it that my CYA level is 40 now for SLAM purposes. Let's hope I can finally get on top of the algae. Think I am getting there - water looks different already and that's just from today!