The impossibility of calculating how much CYA I need -- ideas?

[singerteacher]

I closed the pool with CYA at 33 last year. I have often opened to 0 CYA, but not this year ...

This year, when I tested the water at opening, it was not clear (so, not 0). But, it was also not cloudy enough to read the lowest number on my Taylor test kit, which is 30. So, the number is somewhere between 1 and 29.

With this weird range of 1 - 29ppm of CYA, I really have no idea how to figure out the right amount of CYA to add. All of the threads on TFP about adding CYA assume that you're able to figure out how much CYA is in your pool.

Is there any way to figure out the CYA in this situation?

This is a real problem with all of the test kits! As TFP members, aren't most of us aiming for CYA in the 30-40 range? The tests go so much higher than needed for people with that goal, and leave the most important range out by not enabling a reading from 1 - 30 (or 1 - 20 on some kits).

I could guess at my number, but let's say I guess 5 and it's really 25. My CYA would wind up 20ppm more than ideal. Complicating the situation further is the issue of CYA not showing up on test results for a week ...

Right now, I'm thinking I should guess 15, add that amount, and wait a week to test again. Does this seem reasonable? Is there another way?

 

[triptyx]

Use PoolMath to calculate going from 0 to 10 CYA. Add that amount via the sock method, wait a day, then retest. It's ok to step up in increments until you get a readable number. Make sure you're using the sock method - don't just pour it in the skimmer. Wait long enough between additions to be sure it's all dissolved.

The problem with the CYA test is that it's fickle and hard to read. There just isn't a good method of testing CYA in the water that is consumer friendly - so it's more about difficulties of chemistry than about a deficiency in the test tube.

Ending up at 40ppm isn't a terrible thing, you just keep your chlorine a little higher. I keep my pool at 50ppm due to strong sun, and I know a fellow TFP Expert nearby that uses 80ppm! As long as you're dosing for the correct chlorine level for your CYA, your pool will be great.

 

[singerteacher]

I've read in a couple places on TFP that CYA readings aren't accurate for a week. Is that not true? Can you test daily, as long as you fully dissolve the CYA?

 

[tim5055]

I've read in a couple places on TFP that CYA readings aren't accurate for a week. Is that not true? Can you test daily, as long as you fully dissolve the CYA?

This is one of those areas that has “evolved” as we watch the results of more members joining and reporting results year after year. If you want to be conservative you can wait two days to test, but we no longer say you must wait a week. This is predicated on using the sock method where you can tell when all the CYA is dissolved.

 

[singerteacher]

Great! Thanks so much.

 

[pookiesunshine]

based on my experience using sock method, i would wait at least two days between doses. If you dont mind consuming your cya test reagents, test yours each day after an addition to see how YOUR system behaves; then you will know how long YOU should wait. the first time you should not have to test more than 3 days after adding cya if using the sock method. jmo.