CYA Question

[AdamS]

Hi Everyone,

I tested my CYA last night and there appears to be a dramatic decrease, I started over 100, got to 96 and last night I tested at 60; I had a wild couple of days (see my previous thread) and did 2 small drains and refills, could that have lowered it this much already? Does testing at night affect the scores? You keep putting drops in until black dot is completely gone, correct?

Also, how do you know if you are losing too much water (like a leak) or if it is from kids swimming/evaporation/etc?

Thank everyone!

 

[Patrick_B]

Depending on a few things loss of 1/4"-3/8" is not unusual. Yes light affects the Cya test, but if it's bright indirect light, the number ought to be pretty good. Try to test in, or mimic the suggested lighting which is direct Sun, at your back, test tube about waist high.

 

[carpenter333]

For a leak you can do the evaporation test. Fill a bucket and mark your line, same for the pool and take a measurement of the loss of each of 24-48-72hrs. The results should mimic each other.

Depending on your definition of a small drain and refill the CYA could effectively have reduced by a good margin.

 

[tim5055]

You keep putting drops in until black dot is completely gone, correct?

It appears everything was answered but this....

Yes, you slowly add the solution to the viewing tube until the black dot just goes away. The trick I learned here it to thne pour it back from the viewing tube into the mixing bottle and do it again. I generally do it three or four time to make sure I'm getting a consistent reading.

As a matter of fact, I did it this week to discover my CYA was now down to 40. I may even turn of the Stenner Pump and dust off the tab floaters for a week out of town I have coming up.

 

[JasonLion]

Doing the CYA test in artificial light will result in the test reading mistakenly high. Indirect sunlight is important for the test to be correct. The brighter light makes it easier to see the black dot, meaning you fill the tube to a higher level, and thus get a lower reading. The test is calibrated for indirect sunlight and will give incorrect results in artificial light.

 

[BoDarville]

Yes, you slowly add the solution to the viewing tube until the black dot just goes away. The trick I learned here it to thne pour it back from the viewing tube into the mixing bottle and do it again. I generally do it three or four time to make sure I'm getting a consistent reading.

I do the same thing.

The CYA test is the most subjective test in the lot. Here are more detailed instruction on how to perform this test properly:Extended Test Kit Directions See post #8.

Doing the CYA test in artificial light will result in the test reading mistakenly high.

For the benefit of everyone reading this thread, this statement is one of the reasons pool store testing is often inaccurate, especially the CYA test. Pool stores read this under artificial light. After I first joined TFP, I took a sample to a nearby pool store and had then run a full suite of tests, just for grins. Their CYA measurement was twice what mine was. Another reason we say to trust your own test results.

 

[tim5055]

For the benefit of everyone reading this thread, this statement is one of the reasons pool store testing is often inaccurate, especially the CYA test. Pool stores read this under artificial light. After I first joined TFP, I took a sample to a nearby pool store and had then run a full suite of tests, just for grins. Their CYA measurement was twice what mine was. Another reason we say to trust your own test results.

Funny, but when I purchased the house with a pool I went to two different pool stores. Both told me my CYA was between 80 - 90. I still remember the guy from the store where they like me (I bought a spa and my M5 from them) telling me in January that it was 95, he thought that a little high for the end of the winter.

When I purchased my own test kit I discovered 200+

 

[AdamS]

Thanks everyone; how often do you test your cya?

 

[Patrick_B]

Not often unless you change out a large amount of water. I test a lot, so I'll test a few times in the front of the season, then maybe a few times more until close. Many test perhaps only three times. Start, middle, and end of season which really is enough in most cases.

 

[AdamS]

How does topping off lost water effect CYA? Also does rain effect CYA? Thanks everyone...

 

[tim5055]

It depends on how the water was lost. When water evaporates the CYA stays in the pool.

But, splash out, the water that leave in your swimsuit, back-washing or any other occurrence that take the total water solution out of the pool reduces CYA