Pool won't hold chlorine/visual etching starting

[katwar]

I started noticing what appears to be almost a yellow grainy texture throughout my pool in the past week or so. It's not yellow algae. It's literally like thousands of little yellow dots. It's through entire pool, walls and floor. I tried brushing and vacuuming to no avail. I have had no issues with pool chemistry until ironically a week ago. I shocked my pool four days ago and for grins and giggles I added some Jack's Yellow Stuff immediately prior to shocking. Rechecked levels yesterday and there was no chlorine. Shocked pool again yesterday. Checked all levels today. Using a Taylor K-2006 (FAS-DPD) test kit, here are my results from today:
Chlorine - 0
pH - 7.4
Alk - 60
Calcium Hardiness - 210
CYA - 110

Water is crystal clear. Current pool temp is 90 degrees. Thought the high air temps might be eating away at the chlorine, but not like this. My CYA has always been extremely high consistently since I started testing after my pool fill last year after getting new plaster (only owned this home for a year). We've had very large amounts of rain in Houston and I have drained excess water big time over the past several months. And still have a very high CYA.

The Taylor test kit included a Taylor "watergram" water balance calculator. My resulting "saturation index" is a -0.5. Yes, that's a negative 0.5. According to the calculator, it says any index less than -0.3 "may be corrosive to concrete, plaster, or metal surfaces". And I'm guessing the visual distortion on my walls and floor is the beginning stages of etching.

I'm at a loss. I've never had zero chlorine along with slightly low pH and Alk and fairly normal calcium hardiness (which may be due to all the shocking recently). I am wide open for suggestions on how to turn this problem around.

IG, 23k gals, new plaster 2014
Hayward DE model 4820 filter, Hayward Super II pump, Pentair Chlorinator #320 - all new in 2014
Kreepy Krauly cleaner, one skimmer, single drain pool floor, city water

 

[tim5055]

Welcome to TFP!!


We do not "shock" our pools on a regular basis, we maintain proper FC to CYA ratios and we follow the SLAM Process when there is a problem. I'm going to assume you have been using CalHypo to shock? Air temperatures do not "eat away" chlorine. Two things do, organics in the water and UV from the sun. With high CYA you can probably rest assured you have something growing in the water that will need you to SLAM. But, to SLAM you have to get the CYA down to a reasonable level.

You say you have low pH, but 7.4 is fine.

Next, 100 is the limit of the CYA test, so at this level we are unsure if it is 100 or some number above 100. Don't equate “just a little over 100” to a number, the tube is not marked for such extrapolation. At this point I would recommend at least a 33% water exchange to get the CYA down. For vinyl lined pools leave at least one foot of water in the shallow end to keep from floating the liner and all pool owners are cautioned that in areas with a high water table lowering the water too much can “float” the pool out of the ground.

 

[kimkats]

First off HI! I am glad you have a good test kit. That will make things MUCH easier!

I am going to link you to a chart about FC and CYA

Pool School - Chlorine / CYA Chart

As you can tell from the chart your CYA is way high meaning you need a LOT of bleach to overcome it.

I have to wonder if you CYA is even higher than you think it is.

Have you seen pool math?

http://www.troublefreepool.com/calc.html

It is a wonderful tool to help you know what to do to keep your pool balanced.

What you need to do for starters is drain some of your water. Pool math will tell you how much. Once you have your CYA in line things will be much easier and we can start working on the yellow dots.

Kim

 

[gary300]

Yes, draining significant water is your only way out of your current situation. Then start over and follow the TFP method. You won't have this problem again. You are lucky you live in an area with abundant water and can drain and refill you pool without much consequence. I live in S Cal, and can't even think about draining thousand of gallons of water without big penalties.

 

[katwar]

Thanks so much for your reply. And I don't typically shock my pool as frequently as I did this past week. Just needed to see if pool was indeed non-responsive to any level of shock. I usually only add shock when my chlorine levels are below 200, which during the summer months is about every 3, sometimes 4 weeks. I do not use CalHypo to shock. I've honestly never heard of it. I've been using Leslie's granular shock for the past year with no issues whatsoever on chlorine levels or any levels other than CYA.

And I should have been more specific about my air temp statement. When it's hot out, the UV levels are usually high as well, and that's what I meant.

I did indeed extrapolate the 110 CYA reading. The level was just sooo close to the 100 mark, but only a tiny smudge below it, so I called it 110. And I understand the gauge is not meant to read for levels above 100.

When I said low pH, my level has always been 7.6....always. So it was strange to see it down to 7.4.

I have an in-ground pool. I did my first CYA reading about 2 weeks after the initial pool fill after having it re-plastered when I purchased the home a year ago. It was around 80 at that time (I kept my scribbles from it). A month later it was at 100 and has basically sat at or barely above the 100 mark. Over the past few months, I have drained an average of 5" a week from the massive amounts of rain we've had. Additionally, I have been backwashing every 4 weeks or as my pressure gauge indicates I need to, and then refilling. I was kind of under the impression that all of the rain water would also help dilute the CYA levels. I was hopeful all of this water turnover would inevitably lower the levels, but it obviously didn't.

I will go read about the SLAM process. It sounds like I need to do a fairly substantial draining and refill. I will see if that will help get the CYA down, and if so see how long it will stay down. I'm sure the info is out there somewhere but I would be curious to better understand how the CYA accumulates in the water to begin with. I will also look into the other brand of shock you mentioned.

And let me ask one more quick question. Is it hypothetically possible for shock to "go bad"? I have always worried that by storing it in my shed in the backyard that our high humidity levels here might have an effect on it.

Thank you so much for your helpful information.

Welcome to TFP!!


We do not "shock" our pools on a regular basis, we maintain proper FC to CYA ratios and we follow the SLAM Process when there is a problem. I'm going to assume you have been using CalHypo to shock? Air temperatures do not "eat away" chlorine. Two things do, organics in the water and UV from the sun. With high CYA you can probably rest assured you have something growing in the water that will need you to SLAM. But, to SLAM you have to get the CYA down to a reasonable level.

You say you have low pH, but 7.4 is fine.

Next, 100 is the limit of the CYA test, so at this level we are unsure if it is 100 or some number above 100. Don't equate “just a little over 100” to a number, the tube is not marked for such extrapolation. At this point I would recommend at least a 33% water exchange to get the CYA down. For vinyl lined pools leave at least one foot of water in the shallow end to keep from floating the liner and all pool owners are cautioned that in areas with a high water table lowering the water too much can “float” the pool out of the ground.

 

[katwar]

Tim, one more thing I just thought of. It seems like I read somewhere that using granular shock vs liquid bleach can in and of itself cause CYA levels to increase. Should I perhaps try liquid bleach for a few months and see how that goes?

- - - Updated - - -

Kim,
Thank you so much for the links. I was just saying to Tim that I would like to better understand how CYA forms and accumulates to begin with. And the math link will be a great resource for determine just how much water I will need to drain. You mentioned "bleach". Do you recommend liquid bleach over granular shock when my chlorine levels get low?

Kathy

First off HI! I am glad you have a good test kit. That will make things MUCH easier!

I am going to link you to a chart about FC and CYA

Pool School - Chlorine / CYA Chart

As you can tell from the chart your CYA is way high meaning you need a LOT of bleach to overcome it.

I have to wonder if you CYA is even higher than you think it is.

Have you seen pool math?

http://www.troublefreepool.com/calc.html

It is a wonderful tool to help you know what to do to keep your pool balanced.

What you need to do for starters is drain some of your water. Pool math will tell you how much. Once you have your CYA in line things will be much easier and we can start working on the yellow dots.

Kim

- - - Updated - - -

Gary,
I feel sooo incredibly bad about the situation for all of you in S Cal. Truly I do. We're just griping and complaining about all of the rain here and you guys are desperate for it. I was dreading getting my first water bill after my pool fill but it was a whopping $90 for approximately 23k gallons. So I certainly don't mind having to drain my pool completely if need be, though it's just a pain to do. But way better than having to have my pool re-plastered again for sure.

Kathy

Yes, draining significant water is your only way out of your current situation. Then start over and follow the TFP method. You won't have this problem again. You are lucky you live in an area with abundant water and can drain and refill you pool without much consequence. I live in S Cal, and can't even think about draining thousand of gallons of water without big penalties.

 

[BuckeyeChris]

Just to be clear to the OP: your CYA (stabilizer) levels are high because you are using granular shock. How are you chlorinating on a daily basis, with pucks? Shock and pucks are what cause your CYA to rise, it has nothing to do with the plaster. Yes rain and backwash will dilute the water, but if you are chlorinating the pool in this way, it CYA will always go back up.

This is why most here (except the seasonal folks in the colder states) use liquid chlorine/bleach, as once you get your CYA where you need it, it won't change except for gradual loss to rain/backwash. Always easy to add more than get rid of it.

You said the chlorine is usually around "200". I'm not sure what methodology that is. Most test reference a PPM reading. 3.0 4.5 something like that. See the CYA/FC relationship page in the pool school guides. For a hot and sunny place like Houston, you should target 40-50. Then add liquid chlorine each day to keep above the minimum FC level for your cya. once you've cleared up your issues.

 

[kimkats]

Here is another link for you.

Pool School - Basic Pool Care Schedule

Please note that you will need to "feed" your pool every day. The "food" is bleach/chlorine. They are the same thing. Bleach can be found at Walmart. The Greater Value kind is 8.25% . Some people have a pool store that is easy for them to get to that will let you use their jugs for a deposit to get chlorine that has 11%.

As noted by Chris the shock and pucks you have used in the past have added CYA to your pool. The only way to get rid of CYA is to drain water. Yes rain water will help but some times it is not enough.

I add about 5 to 7 cups of chlorine a night to my pool. I do it at night so it can "work" on whatever might be in my pool from the day before without the sun taking any.

You are already learning so much! Please keep asking questions!

Kim

 

[tim5055]

It is a basic chemistry issue, chlorine must be bound to something to make it stable. In most forms of solid chlorine (DiChlor shock and Trichlor tabs & shock) the stabilizing additive is CYA. So if you have been using pucks and powdered shock you have been driving your CYA up. An added effect of TriChlor is that it is acidic. It's use can drive down pH

CalHypo is another form of granular shock, but in it's case it used calcium to stabilize the chlorine. Use it too much and you drive up the CH levels of your pool and risk calcium scaling.

There is a Lithium based solid chlorine product, but the expense deters it's use.

Now we get to liquid chlorine products, they are stabilized with a minute amount of salt. Tiny amounts of salt we can deal with easily, or even ignore so that is why we are proponents of using liquid products or a salt water chlorine generator as our preferred methods of chlorinating our pool.

We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. What it needs all the time is chlorine.

Please don't take this the wrong way, but some of your confusion is based on old school/pool store methods of pool care. The relationship between CYA and chlorine was identified in the 70's and has been written about in multiple peer reviewed academic papers. The problem is that as with anything else in a market driven consumer economy there needs to be a monetary push for industries to change the way they do things. The pool industry can't make money selling bleach and a pool store can't make money selling you a salt water chlorine generator every five years. There is no profit. So many try to stick their heads in the sand and continue selling shock & tabs.

How much Pool School have you read? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

I think these three articles will clear up a lot of your confusion.

As to your high CYA. As long as your pool is clear and you maintain the proper level of chlorine in the proper ratio to the high CYA you can slowly bring it down if you totally stop using solid forms of chlorine. For you that means keeping your chlorine above 9 with a target of about 15 to make sure it doesn't go below 9 during a sunny hot day. If anything ever starts to grow in the water you will need to do a big drain and refill as it takes a lot of chlorine to follow the SLAM Process with high CYA.

I started with CYA over 200 18 months ago. Luckily I had a clear pool and through aggressive backwashing, a few small partial drain & refills and harvesting rainwater from a roof gutter I have it at 50. It actually went down to 40, but I floated some tabs to bring it back to 50.

To quote Dave, Site Owner of TFP:

Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.

 

[katwar]

Chris,
I am using pucks in an inline chlorinator. And I accidentally put an extra zero on the chlorine level. To clarify, I said that I only shock when my chlorine level gets below about 2.0. My chlorine level until the past week averages between 3 and 4. I'm guessing the high CYA levels have just finally reached the point of "catching up to me" and have just now started showing the visible effects. It's just so odd that I've had no issues with chlorine levels being difficult to maintain, and then bam literally overnight chlorine levels just ceased to exist.

I'm reading all of the articles and info everyone has provided links for. Will likely need some help once I do the drain to make the transition over to liquid bleach. I read somewhere that I shouldn't use a stabilizer/condition in a pool with a DE filter (that may have been in my filter manual). And though I've never needed to use one, I now wonder if the long term high CYA levels will have an adverse affect somehow on my filter.

Kathy

Just to be clear to the OP: your CYA (stabilizer) levels are high because you are using granular shock. How are you chlorinating on a daily basis, with pucks? Shock and pucks are what cause your CYA to rise, it has nothing to do with the plaster. Yes rain and backwash will dilute the water, but if you are chlorinating the pool in this way, it CYA will always go back up.

This is why most here (except the seasonal folks in the colder states) use liquid chlorine/bleach, as once you get your CYA where you need it, it won't change except for gradual loss to rain/backwash. Always easy to add more than get rid of it.

You said the chlorine is usually around "200". I'm not sure what methodology that is. Most test reference a PPM reading. 3.0 4.5 something like that. See the CYA/FC relationship page in the pool school guides. For a hot and sunny place like Houston, you should target 40-50. Then add liquid chlorine each day to keep above the minimum FC level for your cya. once you've cleared up your issues.

 

[katwar]

Kim,
After reading the information at all of the links that have been suggested, my plan is to now do a partial drain and refill. Then I will transition over to liquid bleach. I know NOTHING about using liquid bleach. I've only been a pool owner for a year and am obviously still learning about every aspect of maintenance. The pool is 25+ years old and the former owner says he's not sure just how many gallons the pool is but thinks it's 25-30,000 gallons. When I had the pool replastered, the information on the quote only states 528 sq ft and 92 LF. I don't have the actual measurements but I suppose I could go out and attempt to get some. I did go back to my water bill for my refill last year and it was for 20k gallons. So that kind of tells me right there that's likely what my pool volume is. I wasn't living in the home yet at that time so most of that usage should be for the pool.

You mentioned that when using liquid bleach, I need to feed the pool every day. Currently I am homebound while caring for my elderly mother who is in hospice in my home. But when I return back to work, I will be traveling 10-12 days per month (average 3 days at a time). That was one of the reasons I got the inline chlorinator put in so that I wouldn't have to worry about chlorine while away.

I actually have a couple of gallons of Great Value bleach for laundry purposes. I just went out and looked at the label which says Sodium hypochlorite 6.0% yields 5.7% available chlorine.
I'm wondering if there are different versions of the GV bleach. Regardless, I will look next time I go and get some.

Once I do the refill, is there a formula for determining the initial amount of bleach I will need to add and what is the best way to add it? Should I measure out what I need and pour it into a bucket and splash it in while walking around the perimeter of the pool? And how will I know how much to add each day? Will I need to test my chlorine levels daily then? Or just test for awhile initially and then get the "feel" of how much to add daily? And will this replace the need to ever add granular shock? Sorry for the dopey questions but I'm very detail oriented...LOL.

Here is another link for you.

Pool School - Basic Pool Care Schedule

Please note that you will need to "feed" your pool every day. The "food" is bleach/chlorine. They are the same thing. Bleach can be found at Walmart. The Greater Value kind is 8.25% . Some people have a pool store that is easy for them to get to that will let you use their jugs for a deposit to get chlorine that has 11%.

As noted by Chris the shock and pucks you have used in the past have added CYA to your pool. The only way to get rid of CYA is to drain water. Yes rain water will help but some times it is not enough.

I add about 5 to 7 cups of chlorine a night to my pool. I do it at night so it can "work" on whatever might be in my pool from the day before without the sun taking any.

You are already learning so much! Please keep asking questions!

Kim

 

[katwar]

Tim,
Thank you for this additional terrific information. You mentioned that you had a CYA over 200 and I'm curious what test kit you used to be able to detect a specific reading over 100. I guess it doesn't matter really in that once the level is anywhere near 100 you've got serious issues period. I just asked Kim about the initial transition from pucks to liquid chlorine but I just realized I didn't read the article you suggested on "How to Chlorinate Your Pool". I will go read that next. Hopefully that will shed some light on all of the questions I asked her. Right when I thought I had a good system going that seemed to be working, I realized I didn't have one at all....LOL. It just took time for that bad system to reveal itself as such.

You also mentioned keeping my chlorine above 9 with a target of 15. Dang, that seems really high. If I'm adding liquid chlorine daily, as Kim suggested, would it be necessary to keep the maintenance levels that high? The Taylor tables indicate 2.0-4.0 is ideal. But I think maybe you're recommending keeping it higher so that if the levels do drop, that can't easily drop to a bad level, is that correct?

Kathy

It is a basic chemistry issue, chlorine must be bound to something to make it stable. In most forms of solid chlorine (DiChlor shock and Trichlor tabs & shock) the stabilizing additive is CYA. So if you have been using pucks and powdered shock you have been driving your CYA up. An added effect of TriChlor is that it is acidic. It's use can drive down pH

CalHypo is another form of granular shock, but in it's case it used calcium to stabilize the chlorine. Use it too much and you drive up the CH levels of your pool and risk calcium scaling.

There is a Lithium based solid chlorine product, but the expense deters it's use.

Now we get to liquid chlorine products, they are stabilized with a minute amount of salt. Tiny amounts of salt we can deal with easily, or even ignore so that is why we are proponents of using liquid products or a salt water chlorine generator as our preferred methods of chlorinating our pool.

We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. What it needs all the time is chlorine.

Please don't take this the wrong way, but some of your confusion is based on old school/pool store methods of pool care. The relationship between CYA and chlorine was identified in the 70's and has been written about in multiple peer reviewed academic papers. The problem is that as with anything else in a market driven consumer economy there needs to be a monetary push for industries to change the way they do things. The pool industry can't make money selling bleach and a pool store can't make money selling you a salt water chlorine generator every five years. There is no profit. So many try to stick their heads in the sand and continue selling shock & tabs.

How much Pool School have you read? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

I think these three articles will clear up a lot of your confusion.

As to your high CYA. As long as your pool is clear and you maintain the proper level of chlorine in the proper ratio to the high CYA you can slowly bring it down if you totally stop using solid forms of chlorine. For you that means keeping your chlorine above 9 with a target of about 15 to make sure it doesn't go below 9 during a sunny hot day. If anything ever starts to grow in the water you will need to do a big drain and refill as it takes a lot of chlorine to follow the SLAM Process with high CYA.

I started with CYA over 200 18 months ago. Luckily I had a clear pool and through aggressive backwashing, a few small partial drain & refills and harvesting rainwater from a roof gutter I have it at 50. It actually went down to 40, but I floated some tabs to bring it back to 50.

To quote Dave, Site Owner of TFP:

 

[katwar]

I went in and used the calculator. Here is a screen shot of the results. BUT.....once I do a partial drain and refill, I will of course need to start all over with the calculator.

 

[kimkats]

Details! I LOVE details! Use Pool Math. Here is the link just in case it got lost above.

http://www.troublefreepool.com/calc.html

Note that towards the bottom there is a place to help you figure how many gals your pool holds.

Play with the Pool Math in that link. Do one thing at a time.

Look at this link. It has the levels your pool needs.

Pool School - Recommended Levels

You will need to pour the bleach into the pool at the return with the pump running to make sure it is mixed. Let the pump run for at least 30 mins. after you add the bleach.

I use a measuring cup I bought just for the bleach. I do NOT use this cup to get my water for testing LOL I was having some HIGH FC levels until I figured that one out.

Walmart has started having two "kinds" of bleach------one is "cleaning" bleach and is 6% the other is just bleach and is 8%. Just keep an eye out.

You will test your pool for FC each day or night. You know your life. Pick the time that best fits your life. Use pool math to see how much bleach you need to add to get to your goal.

HUGS! Let me know if I missed anything!

Kim

 

[kimkats]

travel! I forgot about that question-----------

I am glad you have the inline for that OR you can get a SWG that I have a link for!

Pool School - Salt Water Chlorine Generators

So long as you know what the pucks do (add CYA) you can use them. It might mean that you will have to drain water every once in a while to keep the CYA in check.

I tend to keep my CYA on the lower side so I can use pucks when I go on weekend get aways.

For you a SWG may be the best thing ever! If you decide to go that way there are lots of help with that.

Kim

- - - Updated - - -

I went in and used the calculator. Here is a screen shot of the results. BUT.....once I do a partial drain and refill, I will of course need to start all over with the calculator.

Good job using it. It is such a big help for every day life with a pool!

Kim

 

[katwar]

I was reading that liquid chlorine is ultimately the cheapest route and with the higher percentage can reduce the need to purchase "more". I see that Lowes has liquid chlorine for almost half price right now and I am only a mile away from a Lowes. Is this the right stuff and is this a good price?

Shop Kem-Tek 1-Gallon Liquid Pool Chlorine at Lowes.com

 

[BuckeyeChris]

I like this tool
Chlorine Price Per Ounce Calculator

 

[katwar]

Chris, according to the calculator the chlorine at Lowes comes out to .098 cents per ounce....LOL. MUCH cheaper than anything else listed there. Though I entered 12% for the strength, I'm not sure what the actual strength is. Couldn't get the image large enough to read the label. Thanks for that link. Great little gadget.

I like this tool
Chlorine Price Per Ounce Calculator

 

[BuckeyeChris]

still, maybe it's on sale because it's been sitting on pallets for 6 months. high % has a shorter shelf life. Check not only the %, but the date code. There are threads here about it, but it's usually some combo of the year (15, or 5) and the day of that year (like 170, 048). If it is 12.5% and is more than, IDK, 6 weeks old, you should pass. Others may have more insight into shelf life. It depends on where it was stored, which is pretty unknowable.

 

[katwar]

Kim, see my posts above. I posted my calculator results. I need to drain 60% of my pool....hahaha. I also found liquid chlorine at Lowes for $1.51 a gallon. Though I'm now wondering how old it might be. Doesn't keep long, right?

Great info to know about the measuring cup. I can't get out of house again until next Wednesday when my nurses aide is here to watch my mom while I run errands. If I drain my pool today but can't add chlorine until next Wednesday, that wouldn't be good? I'm dying to get this water out of the pool but only have pucks and shock for now. And I don't want to touch the fresh fill water with pucks. It would defeat the whole purpose of draining it.

Details! I LOVE details! Use Pool Math. Here is the link just in case it got lost above.

http://www.troublefreepool.com/calc.html

Note that towards the bottom there is a place to help you figure how many gals your pool holds.

Play with the Pool Math in that link. Do one thing at a time.

Look at this link. It has the levels your pool needs.

Pool School - Recommended Levels

You will need to pour the bleach into the pool at the return with the pump running to make sure it is mixed. Let the pump run for at least 30 mins. after you add the bleach.

I use a measuring cup I bought just for the bleach. I do NOT use this cup to get my water for testing LOL I was having some HIGH FC levels until I figured that one out.

Walmart has started having two "kinds" of bleach------one is "cleaning" bleach and is 6% the other is just bleach and is 8%. Just keep an eye out.

You will test your pool for FC each day or night. You know your life. Pick the time that best fits your life. Use pool math to see how much bleach you need to add to get to your goal.

HUGS! Let me know if I missed anything!

Kim