is my cya dropping too much?

[sdtfp]

Last year I had CYA around 130. You can see on the chart it was even higher, but I don't think I had the hang of the test yet, so I think 130 was the most accurate. I was goign to change the water this spring, but then my CYA problem went away magically and i started testing around 50 CYA in late april. I read this can happen up here in the NE. Relieved, I didn't change the water and continues on. Now I am testing closer to 30-35 CYA and my chlorine just tested at FC=3 CC=0. Even though I have been trying to maintain in the 6-7 range with minimum of 4. So either my chlorine is dropping to its stable point or now that the sun is coming out, chlorine is dropping faster than I expect. This is my first year using liquid chlorine so I am still calibrating how often and how much I put liquid chlorine.

So first, what is causing the CYA drop and is this normal? The only thing I have been doing recently is I got the CH from 150 to 300 using calcium chloride (94%) from home depot.

Secondly, should I bump up the CYA at this point and with what? I have some chlorine pucks from last year left over and I can dump some in or I can go buy stabalizer. After having 130+ CYA, buying stabilizer seems as foreign as living on a different planet!

Just a bit more background, I had pretty perfect numbers after opening SLAM and the pool seemed to taking care of itself, rather than me trying to figure out how to fix things. Like PH and TA are just on cruise control right now. Water looks amazing. I was losing 1 FC during the day and 0 overnight. Now the warning came in as FC is dropping maybe 2-3 in a day.

 

[Texas Splash]

I'm concerned about the low CH (requiring additions) and CYA loss which might be due to a potential leak. Certainty you'll lose some of those if you lowered the water level for winter prep and along with occasional backwashes, but it seems excessive. Any suspicions about a leak?

 

[mguzzy]

An FC drop of 2-3 /day doesn't sound out of the normal for this time of year for your latitude. In the heat of the summer an FC drop of 4-5ppm/day is not uncommon depending on how much direct sun the pool gets and water temp and all that junk. The CYA drop over the winter could be that much if you get a lot of rain/snow dilution, I don't know if you cover your pool or how you do the winter close. But I expect to start over every year with my CYA when I combine the rain dilutions with the normal degradation the CYA has over time. I like Pat's suggestion to check for a leak if you see multiple levels dropping an abnormal amount over the winter. CYA breaks down over time.. CH not so much.

 

[sdtfp]

I'm concerned about the low CH (requiring additions) and CYA loss which might be due to a potential leak. Certainty you'll lose some of those if you lowered the water level for winter prep and along with occasional backwashes, but it seems excessive. Any suspicions about a leak?

An FC drop of 2-3 /day doesn't sound out of the normal for this time of year for your latitude. In the heat of the summer an FC drop of 4-5ppm/day is not uncommon depending on how much direct sun the pool gets and water temp and all that junk. The CYA drop over the winter could be that much if you get a lot of rain/snow dilution, I don't know if you cover your pool or how you do the winter close. But I expect to start over every year with my CYA when I combine the rain dilutions with the normal degradation the CYA has over time. I like Pat's suggestion to check for a leak if you see multiple levels dropping an abnormal amount over the winter. CYA breaks down over time.. CH not so much.

I think the CYA loss over the winter can be explained by dilution. I was aggressive in keeping the water level low since I was planning on draining the pool. So it was definitely 4-8 drains and the fills with rain water. We got a lot of rain/snow. By the time I opened, I had to add probably like 10 inches of water too, since I had been draining it that often. This winter, I won't be draining as much and plan to open to a pool full of water!

Regarding the leak, I don't think there is any. I had that concern last year over the summer since I was new to the pool and didnt have a feeling for how much the sun is draining. I even had the pool tech add some putty inthe skimmer opening. All that to say that I am very sensitive to leaks and have been watching the water level almost daily now. I'm happy to report that due to (mild) rain, the water level has actually increased over time and there has been no loss in between rain storms. Like I mentioned, it's been cloudy for weeks, so I didn't expect any water loss, but now that the sun is coming out, there might be some going forward.

Regarding the CH, I attribute that to the pool guys not wanting to add CH. I mentioned it to them last year as it was continually testing low and they said they would do something about it. I'm not sure if they added some, but it was towards the end of the season and I figured I'll just take over and do it next season anyways so I didn't pursue it. So there is no way to say that there is much CH loss, since it could have been years withotu any CH addition. The pool guys had no intention of adding any had I not mentioned it!

So I think the main concern is the recent CYA loss. I definitely was not seeing much CYA losses last season as I was very nervous about it for a long time. But they were using chlorine pucks, so they were continually adding CYA. Is it normal to continually add CYA when on liquid chlorine? From what I read here, chlorine pucks are bad and CYA never goes down. But everyone up here uses chlorine pucks and my CYA goes down!

 

[Rancho Cost-a-Lotta]

One note...cold water temps can result in inaccurate CYA test results. Not sure if that's an issue, but when I think of New York, I picture snow in the streets.

 

[Texas Splash]

Is it normal to continually add CYA when on liquid chlorine?

Continually no, but CYA does degrade and disappear at a rate of about 5 ppm per month. So over the course of a few months CYA could conceivably go down 20-30 ppm. Add to that water changes or anything else and it's understandable to have to add some at some point.

 

[sdtfp]

Continually no, but CYA does degrade and disappear at a rate of about 5 ppm per month. So over the course of a few months CYA could conceivably go down 20-30 ppm. Add to that water changes or anything else and it's understandable to have to add some at some point.

okay I did not know that. I'll buy some powder stabilizer from the pool store. I should be aiming for 40 correct? Pool math says "Add 24oz by weight or 25oz by volume of stabilize" Should I do a split app and test before the second app? And is CYA the thing added through a sock?

Maybe I'll just buy some and just keep monitoring the situation. See if I can get to a point where it feels normal. I think I need to add 8 cups of 10% liquid chlorine every day now if the trend continues. Does that seem normal? You guys with bigger pools are you doing a gal of 10% chlorine a day? So 60 gallons in two months? Seems excessive to me.. where are you storing this?

 

[CraigChing]

One note...cold water temps can result in inaccurate CYA test results. Not sure if that's an issue, but when I think of New York, I picture snow in the streets.

This. I don’t trust my CYA results until I get my heater going and am consistently testing 84 degree water. I still test after letting my sample get up to about 70ish degrees early in the season, but I don’t trust the test completely until we’re into the season and the heater is going. I’ve been fighting high CYA since we acquired our pool two years ago, so I test more regularly than most people test CYA.

 

[sdtfp]

This. I don’t trust my CYA results until I get my heater going and am consistently testing 84 degree water. I still test after letting my sample get up to about 70ish degrees early in the season, but I don’t trust the test completely until we’re into the season and the heater is going. I’ve been fighting high CYA since we acquired our pool two years ago, so I test more regularly than most people test CYA.

Wow, this sounds scary. Does CYA test low or high in cold water? Don't tell me that CYA of 130 will be coming back? But that doesnt make sense as water temp has been increasing and CYA has been decreasing. But seems like another reason for me to hold for a bit and see what happens before I add any stabilizer.

 

[CraigChing]

My advice is let your sample warm up to somewhere in the 70s degrees F before testing. The difference isn’t super huge, but you can look at my pool math logs to see the swings I see in the test. I have had super high CYA the last couple of years that I didn’t perform a drain to correct. I’ve just been living with it so long as my water stays clear. I *think* I’m down to 70 now, but I’ll feel better when I see those consistent numbers from tests as my water temp stabilizes. Realize that being further north than most people and draining for winterizing is what allows me to maintain as I have.

 

[Texas Splash]

Yes, if your water temp is still chilly, bring the sample indoors for a few to warm up to room temp then go back outside for a viewing test. Yes, stabilizer is what you will be looking for. We put it in a sock, let it soak for about 30 min, then squeeze it all out like mush. My pool is just under 18K and a 1/2 gallon of 10% was my pool's daily diet during the summer before I got my SWG.

 

[mguzzy]

Yes, if your water is below 70 deg it will affect your CYA test. I find either holding the bottle in my closed hand will help warm it up or let it sit in the sun while I am running my other tests.

 

[sdtfp]

Yes, if your water temp is still chilly, bring the sample indoors for a few to warm up to room temp then go back outside for a viewing test. Yes, stabilizer is what you will be looking for. We put it in a sock, let it soak for about 30 min, then squeeze it all out like mush. My pool is just under 18K and a 1/2 gallon of 10% was my pool's daily diet during the summer before I got my SWG.

Yes, if your water is below 70 deg it will affect your CYA test. I find either holding the bottle in my closed hand will help warm it up or let it sit in the sun while I am running my other tests.

Okay, I don't think my water is the cold. Definitely surface water temps are above that. And I do let it sit for a few minutes. I'll let it sit longer next time.

I did an OCLT and no chlorine was lost. It definitely looks like the sun is taking up the chlorine. I was trying to keep it around 5.5 to 6.5 when CYA was 40. But now that seems difficult with CYA of 30-35. and more sunlight. I'll try to keep it 4-5 FC now and see how difficult that is to keep. So when I hit 3 i'll bump it to 5. See if I can make that into a routine. Then in future I will bump CYA to 40 and go back to bumping it to 6 when it hits 4. Then as things get hotter, I'll have to bump up by 3 or 4 FC per day.

 

[mguzzy]

I find my warmer surface temp water is only in the top few inches and if we are following the testing instructions we should be taking the water from 18 inches.. below the "warm zone". In NYC.. if you don't have a heater.. I expect your pool is on the chilly side still this time of year.

Think of your chlorine usage like a bell curve with the peak in mid July when the sun is highest in the sky and the swimmers are at their max. your FC demand will rise through the summer, peak and then tail off into the fall. So you just need to adjust your chlorine usage to match whatever that curve is for your pool and how much you use it. It really does take a couple of seasons to see the patterns of your pool and testing is your guide.

 

[engrav]

Continually no, but CYA does degrade and disappear at a rate of about 5 ppm per month. So over the course of a few months CYA could conceivably go down 20-30 ppm. Add to that water changes or anything else and it's understandable to have to add some at some point.

Is true here (Seattle). Do not close pool. Add 1g chlorine every 7-10 days over the winter. Water about 40 degrees. Every Fall CYA is 50. Every Spring CYA is < 30 and I add 4# CYA.