Can you lose CYA?

[Vandergraff]

I always understood the main issue was CYA build up over time and the only way to reduce CYA was to drain water and replace it.

For the last 10 years or so our pool has had a CYA of about 40 - 60 (best guess as the test is not really easy to read). We did liquid chlorine in the summer (swim season) and water was perfect and no algae blooms. In the winter we use tabs as solar is off and pool temp low. Always a little surprised each spring that the CYA wasn't higher after using tabs - but everything good.

This year we have had very high liquid chlorine usage (which is getting very expensive with the current cost of chlorine) and testing CYA it seems maybe 10 - 20 (again the I find the test very hard to read to get an accurate result).

Could we really have lost CYA like this? Pool is never drained (on a well and it would be prohibitive to try to refill) just topped up during the summer to replace evaporative loss (but the CYA should stay in pool - correct?)

Are there any more accurate CYA tests than the black dot test? A little reluctant to add CYA until I know it is really low as it will really be hard to lower it if it gets high.

Pool still looks great - but if CYA is low I guess even low levels of chlorine would be working....

 

[duraleigh]

Yes, the CYA test is vague and, yes, CYA can degrade over a period of time.

I would suggest you calculate a 20 ppm dose and add it to your pool. Wait 24 hours and test.

Next, you ultimately need about 60 ppm for the summer months so add a second dose to get to 60. Test again every 30 days.

There are no tests more valid or precise than black dot. Don't worry about it too much and make sure you keep it around 60 ppm.

 

[Texas Splash]

Van, I would also encourage you to update your signature with all of your pool and equipment info. You confirmed using liquid chlorine and solar, but it helps to see everything in your signature. Often times the items in your signature will apply to the question posted. You can refer to our signatures and the article below as examples to help. Have a great day.

Create Your Signature - Further Reading

www.troublefreepool.com

 

[Hoster]

I always understood the main issue was CYA build up over time and the only way to reduce CYA was to drain water and replace it.

For the last 10 years or so our pool has had a CYA of about 40 - 60 (best guess as the test is not really easy to read). We did liquid chlorine in the summer (swim season) and water was perfect and no algae blooms. In the winter we use tabs as solar is off and pool temp low. Always a little surprised each spring that the CYA wasn't higher after using tabs - but everything good.

This year we have had very high liquid chlorine usage (which is getting very expensive with the current cost of chlorine) and testing CYA it seems maybe 10 - 20 (again the I find the test very hard to read to get an accurate result).

Could we really have lost CYA like this? Pool is never drained (on a well and it would be prohibitive to try to refill) just topped up during the summer to replace evaporative loss (but the CYA should stay in pool - correct?)

Are there any more accurate CYA tests than the black dot test? A little reluctant to add CYA until I know it is really low as it will really be hard to lower it if it gets high.

Pool still looks great - but if CYA is low I guess even low levels of chlorine would be working....

I am also experiencing the same - i.e., CYA is not increasing at all, in fact, decreasing even though I added like 15lb over 3-4 weeks. And Yes, I have been adding 20+ gallons of liquid chlorine....would be interesting to get some expert opinions...

 

[Vandergraff]

Yes, the CYA test is vague and, yes, CYA can degrade over a period of time.

I would suggest you calculate a 20 ppm dose and add it to your pool. Wait 24 hours and test.

Next, you ultimately need about 60 ppm for the summer months so add a second dose to get to 60. Test again every 30 days.

There are no tests more valid or precise than black dot. Don't worry about it too much and make sure you keep it around 60 ppm.

Thanks bought some today and will add a 20 ppm dose and measure in 24 hours as you suggest

 

[cdadams1223]

The best method I've read on here is the following: mix up your 50/50 dose of pool water and your reagent, shake it 30 seconds, fill the CYA test tube up to 100, take a quick glance at the dot (don't stare), still see it, fill up to 90 and repeat the process until you cannot see the dot. Make sure you're holding the tube at waist height when you glance down into it and also the sun should be at your back. This works so much better for me than holding it in front of me at waist level and slowly filling it. Doing it that way causes you to stare at the dot which then comes fixed in your vision.

 

[Vandergraff]

OK - it seems I am going to have to be careful adding the cyanuric acid to the pool as it is - well an acid...

My solar panels have copper tubing - so I don't want low PH water running through them.

For now I will try 1lb (probably about 1/3 of the first dose) of the powder in a skimmer sock with the pump running overnight (so without the water flowing through the solar panels). Hopefully this will have dissolved by the morning and I can repeat again tomorrow night etc. If not I guess a sock or similar in the pool on the other side to skimmer should be OK (CYA should be diluted by the time it gets to the skimmer) but I am guessing this will take some time to dissolve.

I know the other option is to turn the solar off for a few days - but we have no other way to heat the pool so it loses temperature very quickly and my wife would not be happy with no pool access for a few days....

(note what I got at the pool store says its isocyanuric acid - is this the same thing as cyanuric acid?)

 

[cdadams1223]

(note what I got at the pool store says its isocyanuric acid - is this the same thing as cyanuric acid?)

It's the same thing.

 

[Vandergraff]

The best method I've read on here is the following: mix up your 50/50 dose of pool water and your reagent, shake it 30 seconds, fill the CYA test tube up to 100, take a quick glance at the dot (don't stare), still see it, fill up to 90 and repeat the process until you cannot see the dot. Make sure you're holding the tube at waist height when you glance down into it and also the sun should be at your back. This works so much better for me than holding it in front of me at waist level and slowly filling it. Doing it that way causes you to stare at the dot which then comes fixed in your vision.

Will try that - thanks.

Yes it seems I can't unsee the black dot once I see it!

 

[Vandergraff]

For now I will try 1lb (probably about 1/3 of the first dose) of the powder in a skimmer sock with the pump running overnight (so without the water flowing through the solar panels). Hopefully this will have dissolved by the morning and I can

Seems like this is going to work. 1lb had dissolved in the skimmer sock within a couple of hours. Added another 2lbs which should dissolve overnight.

Will test CYA tomorrow evening to see where it is - and add more if needed.

 

[Vandergraff]

OK this did work - all 3lbs of CYA dissolved in the skimmer sock last night and testing CYA tonight read about 40 ppm and FC levels still good at the end of the day.

Next, you ultimately need about 60 ppm for the summer months so add a second dose to get to 60. Test again every 30 days.

Last few years have been in 40 - 60 ppm range (more likely 40 - 50 ppm) so I am wondering about the suggestion to get to 60 ppm and Pool School recommendation for ideal levels for a plaster pool with liquid chlorine at 40 - 50 ppm with 50 - 60ppm acceptable maximum?

Should I increase CYA a little more or stay where I am. I am also going to get the CYA 50 ppm standard solution to check my ability to read the test.

Summer pool water temps are ~ 80F in the morning up to +85F in the evening after the the solar heating (yes we like our pool warm). Fill water from well has high TA (470) so I just focus on keeping PH and FC good using Pool Math App and muratic acid and liquid chlorine every evening. TA unmanageable because of the well fill water.

Water clarity and feel has been great using this method.

I would also encourage you to update your signature with all of your pool and equipment info.

Done

 

[duraleigh]

Keep your CYA right where it is for now, If your daily chlorine loss exceeds 3-4 ppm, I would encourage you to go to 60 ppm CYA.

 

[Vandergraff]

Keep your CYA right where it is for now, If your daily chlorine loss exceeds 3-4 ppm, I would encourage you to go to 60 ppm CYA.

After testing with the CYA 50 ppm standard solution to check my ability to read the test I am pretty sure I am around 40 for CYA in the pool (testing with the standard solution and knowing the answer I would have been estimating somewhere between 40 - 60 for the standard solution).

So I added another 1lb of CYA to get CYA around 50.

Daily chlorine loss is more like 2 ppm in hot sunny weather and pool at 87F in the evening after solar heating during the day.

 

[cledee]

I am also experiencing the same - i.e., CYA is not increasing at all, in fact, decreasing even though I added like 15lb over 3-4 weeks. And Yes, I have been adding 20+ gallons of liquid chlorine....would be interesting to get some expert opinions...

I would check to make sure you don't have ammonia in you water. If you don't then it's probably for the following reasons.

You can lose CYA by splash out, by draining, by chlorine breakdown in sunlight or if the water temperatures are above 90+.

It's possible to lose 10ppm CYA per month due to splash out, chlorine breakdown and water temperatures above 90.

 

[Hoster]

I would check to make sure you don't have ammonia in you water. If you don't then it's probably for the following reasons.

You can lose CYA by splash out, by draining, by chlorine breakdown in sunlight or if the water temperatures are above 90+.

It's possible to lose 10ppm CYA per month due to splash out, chlorine breakdown and water temperatures above 90.

Thanks for the input. Probably chlorine breakdown is the main culprit as the water temp has been around 85 at the peak. Another "funny" thing is that my CYA was around 30PPM, added less than 2 lb, then 2 days later found my CYA to be 80. Not sure my additions in the past (3-4 weeks ago) finally decided to show up??

Just difficult to manage / balance chemicals this season for some reason - I drained 1/2 before I closed last season (to repair rust behind the liner) then the rain / snow filled the rest when I opened. Not sure this has anything to do with this season's difficulties.

 

[DBissett]

I would check to make sure you don't have ammonia in you water. If you don't then it's probably for the following reasons.

You can lose CYA by splash out, by draining, by chlorine breakdown in sunlight or if the water temperatures are above 90+.

It's possible to lose 10ppm CYA per month due to splash out, chlorine breakdown and water temperatures above 90.

I did not know this about CYA and water temp and glad to learn it. With daily temp range of 80/100+ our pool has averaged about 95 degrees for almost two months and I've been fighting to keep the CYA high enough. I think I've added 12 lbs of dry stabilizer, a gallon of liquid a few days ago and have another gallon on order. Chlorine consumption is about 2qts/day now but's been quite a bit higher in previous weeks. Next year I plan to shade the pool as these Houston summers really do a number on it.

 

[cledee]

I did not know this about CYA and water temp and glad to learn it. With daily temp range of 80/100+ our pool has averaged about 95 degrees for almost two months and I've been fighting to keep the CYA high enough. I think I've added 12 lbs of dry stabilizer, a gallon of liquid a few days ago and have another gallon on order. Chlorine consumption is about 2qts/day now but's been quite a bit higher in previous weeks. Next year I plan to shade the pool as these Houston summers really do a number on it.

This is why you have to test the CYA monthly and adjust as needed. I originally thought the same with CYA and thought I could only lose it with splash out or draining, but because we have a heater and keep the water between 85-90, I would notice a nearly 10ppm drop per month between July and August. I usually just add around 1.5lbs of Trichlor in a floater to replenish the lost CYA.