adjust cya before or after shocking

sorry to report that I am back with algae problems. My test results at 6:30 pm today were FC= 6, CC = .5, pH = 7.4 and TA = 70. I've been adding CYA through stocking since the time I thought I had previous algae problem resolved. I was out of town for a week but tested on 5/4 and pH was 7.6. I starting dosing again with CYA on 5/5. I'd turned my SWG on again when I thought algae problem was taken care of but FC had stayed high 11, 10, then 9 on 5/5 so I turned SWG off. So,without SWG, FC was coming down and was at 6 today. But now I have algae again): What caused it? Is it because I forgot to test pH and keep it at 7.5-7.6? Should I have left SWG on? Trying to figure out where I went wrong. Also, do I need to raise pH before I shock again? I plan to use bleach to shock.
Thanks.

If you have algae again, it's because you either 1) let the chlorine get too low, or 2) never killed it off completely before allowing your chlorine to come back down. It has nothing to do with your pH. Your pH is fine where it is--you just need to raise your chlorine back up to shock level (best to do that with bleach instead of your SWCG). How high shock level is depends on your current CYA level. Do you have the test kit yet so you can test your CYA?

The chlorine has not been below 6 in at least a month so I guess the algae wasn't completely dead...tho I tested and went back and forth with the forum experts till we thought it was.
So, I will test CYA in the morning then check pool calculator to find amount of bleach needed to shock then test and keep at shock levels and test and on and on. Does that sound right?
Thanks.

Yes. That is the correct plan. Don't test CYA too often, though, or you'll waste the reagents. Did you get the K-2006 kit yet?

You ( and Watermom of course ) are right. Is the algae in the water or on the walls and floor? Brushing the pool will help get the chlorine to the algae stuck on pool surfaces.
So, the recipie is:
Bring your FC up to shock level for your CYA and keep it there as best as you can by testing and dosing as often as you can.
Shut off the SWCG and run the pump 24/7.
Backwash the filter when pressure climbs 8-10psi over clean pressure.
Brush the pool, especially where algae is visible.
When you have less than 1 ppm FC loss overnight and minimal CC (less than 0.5 if using the 10ml sample size), keep the FC at shock for one more day.
Please use the "Edit your signature" link in Watermom's sig to add your pool's particulars to your signature.

Be patient.
Don't worry, you'll get this under control.
Keep us up to date.

I scanned through this thread, and could not find a reported CYA level . . . .

On 04-15-2012 at 05:02 PM on page 7 of this thread OP posted CYA of 30, since then has been adding CYA in a stocking.

CYA = 40 this morning so according to "Best Guess" I need to shock at FC = 15 and stay there or above.
Dave, algae is mostly on the bottom and lower sides of pool. Thanks for recapping the steps.
I'll edit signature.
Thanks!

Do you still have the dichlor? You can use that to move toward your shock level and your CYA goal but remember as CYA goes up so does your FC goal for shock and normal operation.
How much dichlor do you have on hand?
Is there still CYA in the stocking?
Do you bleach / Liquid chlorine on hand? How much?

No more dichlor on hand. There is still CYA in stocking but I have removed it from the pool. I don't have any bleach on hand so was heading to the store. Should I use dichlor or bleach? I haven't done a cost analysis. If I use dichlor, do I need to raise pH to 7.6 before I start?

Use bleach, it'll be eaiser, unless toting it around is an issue.

Quote:

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Originally Posted by Kateyru

CYA = 40 this morning so according to "Best Guess" I need to shock at FC = 15 and stay there or above.

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Yes! And, brush all the algae spots AFTER adding a chlorine dose.

(Thanks, Dave!)

no problem toting bleach...easier than toting 40 lbs. bags of salt. yes, brush, brush, brush! My new mantra: Yes I can...defeat algae!!!
Thanks!

Your pH is fine where it is. Don't bother with adjusting it until it needs to be. If you get down to 7.0, then just adjust it up with Borax.

In a 22K gallon pool, 5.5 gallons of 6% bleach will get you up to 15 ppm. After that, each 1.5 quarts will raise your FC by 1 ppm, so you can use that as a guide. With your SWCG off, raise your chlorine to 15 ppm, (I would do this in the evening), then test in the morning and sometime during the day, adding whatever amount of bleach necessary to get back over the 15 ppm mark. Brush the pool daily, ( I would do this in conjuction with your bleach additions) so that you're knocking all the algae loose, getting better exposure to the chlorine. Hold that 15 ppm until you're not losing any chlorine from night time til in the morning, and then you can let it drift back down. Keep the pump running (but not the SWCG) and keep an eye on your filter pressure, so you can backwash it as needed (when the pressure rises 8-10 psi over your clean pressure).


This procedure is not difficult; but it does take persistence on your part to get it cleared up. If you don't fully get rid of the algae before you let the Cl levels come back down, or if you aren't consistent about maintaining your Cl levels, then you're going to be fighting algae all summer.

Okay, I think I've got it. Added 5.5 gallons of 6% bleach this evening then brushed all the sides and as much of the bottom as I could reach. SWG is off and pump set to run. I'm going to look back over the posts from my last attempt to shock and try to figure out where I went wrong. Maybe I didn't go long enough with FC at 15 and not losing any chlorine from pm till am.
Thanks.

It's clear to me now that I didn't keep FC at or above 15 (shock level) long enough even though I got to the point where I didn't lose more than 1 ppm and CC was < .5 from evening till morning. The FC was just too low to kill all algae. Once FC got down to 6, the algae was obvious. Thanks, Aylad.
Question for Aylad--why are the chlorine amounts you said are needed to shock different than what I calculated with the Pool Calculator?
Thanks.

Quote:

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Originally Posted by Kateyru

Question for Aylad--why are the chlorine amounts you said are needed to shock different than what I calculated with the Pool Calculator?

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I'll answer that:

(1) The Poolcalculator is NOT ours, but it is based on Chem_Geek's chlorine spreadsheet, which laid out the analytical basis for my Best Guess chart, which was partly analytical, but partly based on my field experience.
(2) Both the calculator, and Chem_Geek's spreadsheet attempt to be EXACT. We don't, and not by accident. Pool volume calculations, test kit errors, and dosing errors all come together to make the sort of exactness suggested by those tools, unreachable in practice.
(3) So . . . we try to give estimated doses, that are calibrated to avoid problems. In practice, this means we estimate CHLORINE doses HIGH, and everything else LOW.

What Janet did was give you a dose for 15 ppm MORE chlorine -- in practice, that's the right thing to do, since she didn't know how much chlorine you'd have in your pool, when you added your dose. But, when you used the pool calculator, you probably took the chlorine level from your LAST test -- even though that value was unlikely to be correct by the time you added more chlorine -- and entered that into the calculator. So, the calculator told you how much MORE chlorine you should add to get there.

Mathematically, that's correct. But, practically that's wrong.

Richard (Chem_Geek) doesn't agree with me on this point. But, I think that's partly personal error. Richard is EXTREMELY careful and meticulous in his personal habits, and tends to assume others will be, too. He recently told me he'd NEVER had even a drip when using muriatic acid, as we discussed how we should tell people to add acid to pools. If anyone else had told me that, I'd assume they were exaggerating or outright lying. But, I'm pretty confident that he may be the only pool person who is that precise.

So, the pool calculator and his spread sheet work out for HIM, as exactly as they imply. Of course, if there's another pool owner in the USA as exacting and precise as he is, I'd be surprised.

My view is that the pool calculator is more exact in theory (apart from a few errors it has embedded), our approach is more correct in actual practice.

Thank you so much for taking the time to explain that. Makes perfect sense!

I kinda screwed up as I ran out of titrating reagent this morning BEFORE I could test. Should have been paying attention to that... I ran to the store and got distilled water to test that way. My best guesstimate using distilled water testing is that FC is at least 15. I actually did test FC before I added bleach last night so I could be fairly accurate with Pool Calculator calculations but then ended up adding a total of 5.5 gallons of 6% because that's what Janet said to do (and now I understand why). So, last night, FC should have been at about 21.5. All that to say that I think FC is at least 15 now. So, should I add more bleach now for insurance? If so, how much? Should I be testing pH when I test FC?
Thanks!!!

Leave the pH alone and don't worry about it. With the chlorine level that high, the pH result won't be accurate anyway, but if you're just using bleach, the pH is not going to change enough to be an issue. Focus on your chlorine and forget about the rest for awhile.

If you "add more bleach for insurance", then you may just be wasting bleach, so I wouldn't do that. Test your water again, estimate the level, then add bleach if you're under the 15 ppm mark. (And if you did get to 21 ppm last night, it won't hurt the pool--it would just be more available chlorine to work on the algae).

Ignore previous post as I think I am muddling through. Here's another related question. I reviewed the thread about my previous efforts to get rid of algae. Quick recap: in process of shocking, and after turning off SWG, FC test results were:

4/11/12, 5PM, FC =15.5
4/12/12, 6AM, FC =14
4/13/12, 7AM, FC =10
4/13/12, PM, FC = 8
4/14/12, AM, FC = 7
4/14/12, PM, FC = 7
4/15/12, AM, FC = 7
4/15/12, PM, FC = 4.5
4/16/12, PM, FC = 7.5
4/17/12, PM, FC = 9.5
4/18/12, PM, FC = 8
4/19/12, FC = 10.5
4/20/12, PM, FC = 8.5
4/21/12 PM, FC = 7
4/22/12, PM, FC = 4.5 (I turned SWG back on at this point)
4/23/12, PM, FC = 5 (I added 48 oz. of CYA, don't know if I added bleach)
4/25/12, PM, FC = 11.5 LEFT TOWN
5/4/12, PM, FC =10
5/5/12, PM, FC =9 (added 48 oz. of CYA)
5/6/12, Am, FC = 8
5/7/12, AM, FC = 6.5
5/7/12, PM, FC = 6
5/8/12 I"VE GOT ALGAE FOR SURE!
5/8/12, PM, FC = 6.5 and shocking starts

Also, re: test results, just fyi, when tested during shock period, CC was always .05, < .05, or 0.

As I said in previous post, it is clear to me now that I didn't keep FC > 15 long enough.
So, here's my thought/question:

**** Can algae, over time, raise its tolerance to FC? That is to say, if you don't get all the algae when you shock (due to human error or whatever), at some point in time after repeated unsuccessful attempts to shock, will the FC need to be maintained > 3 - 5 ppm in the future to keep algae at bay? I am not a chemist (obviously) and have never had much interest in chemistry but am somewhat fascinated by all of this.
An aside, it seems like there could be some really interesting science projects out of pool water study. I'll have to remember that when my grands are a little older :)

Janet, we were posting at the same time. I remembered (in the middle of the night) that testing pH was moot point when shocking. I've been testing as best I can (as you suggest) and brushing.
You can see from my previous post, that I am not only focused on the chlorine, I am somewhat obsessing...

Once you get the algae killed off, you're going to need to raise your CYA levels to help protect your chlorine from the sun. When that happens, you're going to have to raise your chlorine levels to compensate for that. Look through this thread for some of the sigs that have the link for the "best guess chlorine chart", and that should answer your questions regarding higher chlorine levels.

In looking at your chlorine log, you simply did not sustain the chlorine levels long enough to kill the algae. As we've said many times throughout this thread, you need to get it to the 15 ppm make and keep it there until the algae is dead. By letting the chlorine levels yo-yo up and down like that, you may be preventing further algae growth, but you're not doing anything to kill the original bloom.

I don't really rely on CC readings for algae determination....sunlight and chlorine both help eliminate CC. I have personally seen algae on the side of my pool with a CC of zero. That's why a much more reliable test is to see no chlorine consumption overnight.

I was actually in the process of raising CYA level when the algae made itself known (to me) so I'm clear with that.
I do think I understand most of this now. In my previous shock attack, somehow the focus and comments back and forth got on FC loss from evening till morning coupled with minimal CC. The length of time my FC was at or above 15 ppm seems to have gotten overlooked it.
Many thanks again!

Quote:

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Originally Posted by Kateyru

**** Can algae, over time, raise its tolerance to FC? That is to say, if you don't get all the algae when you shock (due to human error or whatever), at some point in time after repeated unsuccessful attempts to shock, will the FC need to be maintained > 3 - 5 ppm in the future to keep algae at bay?

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I don't know if algae can become more cl tolerant through selection, makes some sense that you may be cultivating a cl resistant algea population. I do know that once you've raised the FC high enough for long enough to kill that population, you won't have to be concerned raising your base cl level for the resistant population as it will be gone. Any new algea that enters the pool will not have been through the selction process and will be no more cl tolerant than all the other algae.

Touching base again. I started my 2nd shock attack on 5/8 after messing up the first time, i.e., I didn't keep FC > 15 ppm long enough to kill all the algae. About the time I started 2nd attack, I ran out of reagent so used dilution testing until new reagent arrived. Using dilution testing then FC testing with K-2006 kit when replacement reagent arrived, I've tried to keep FC at or above 15. So, this is day 12. I was out of town for a couple of days this past week and am aware that FC got below 15 a couple of times. How much of a setback is that? I didn't lose any FC from last night until this morning. My plan, per forum guidance, is to stay at or above 15 for an extra day, that is, 1 full day after no chlorine loss overnight. That would be today if the 2 recent dips below 15 don't have a significant effect overall. Guidance please.
Thanks!

You are right to give it the extra day as long as there is still no more than a 1ppm chlorine loss overnight from sundown to sunup and you don't have a CC reading.

FC was at 17 at 7:30 am. I added 3 qts. of bleach at that time since I knew I would be gone for a few hours. At 1:30 pm, FC was 15. I added another 3 qts. of bleach. At 4:30 pm, FC was 16. I was gone again for a few hours. I didn't add more bleach since it was 4:30 in the afternoon. Got home and checked FC again at 8:30 pm, and it was 13.5. I lost 2.5 ppm between 4:30 and 8:30 in the late afternoon/evening. Seems like a lot. I've added another 3 qts of bleach now (at 8:30 pm). That seemed the way to go rather than worrying about chlorine loss. Is this loss excessive for time of day? Sun sets about 7:30 pm and it's hot (mid 80's) but sun is off the pool by 5:30 pm or so. So, is the loss due to sunlight? Does stubborn, refuse-to-die algae exist???? I feel like I have been shocking for ages.
Thanks.

Bleach loss during the day is likely sunlight. You can really only tell what your non-solar loss is, by comparing late PM to early AM readings.

What is your CYA level?

The last time I checked CYA was 5/8 and it was 40. I've been following Janet's recommendation to focus on FC and not worry about anything else. This morning at 6:30, FC was 16.5 and CC = 0. I had not been checking CC but did today since Watermom said to. I added 3 more qts of bleach and turned SWG on as I was not sure I could get home until late afternoon. Trying to make sure FC stays over 15.

Do you still have visible algae?
Where? What does it look like?

Also, it's probably time to retest your CYA level.

No visible algae. Water looks good, nice and clear. I'll retest CYA this afternoon. Do you think I can let FC drift down or do I need to keep it at or above 15 for another day? Am really hoping for a clean pool by this weekend!
Thanks so much!

Go with another day for added insurance. If after one more day, you still don't lose more than 1ppm overnight and still have CC of 0, let it drift down. But, be diligent about keeping your chlorine levels at appropriate levels based on your CYA reading. (Like Ben said, retest CYA to make sure you know what it is so you'll know needed cl levels.)

Okay, FC last night and this morning were the same and CC was 0. Doing insurance plan today :) If FC and CC are okay from tonight till tomorrow am, I'll let chlorine start the downward drift. CYA was 45 to 50 last night. I'm struggling with reading CYA and trying to accurately recognize "just till black dot disappears." I haven't had problems with chlorine levels in the past but plan to up CYA to 70 to 80 so will be more vigilant and diligent re: chlorine as needed.
thanks again for all the help. I just read "the history" of the forum. I am so glad the forum (and troublefree pools website) exist and very, very glad I found both!

Just don't ever let the chlorine get below 3 ppm, and if you up your CYA any more, then don't let it get below 5 ppm, and you shouldn't have any troubles.

The CYA test is a very subjective test--the best you can do is try to run the test in the same conditions (lighting, distance from tube to your eye, etc) so you can be as consistent as possible.

Glad to know it is very subjective test!

It is definitely the hardest test to interpret.

Ah, you guys, I'm back again with green algae dust ): A quick recap of most recent battle with algae...from 5/21 to 5/24, FC was over 15 until afternoon of 5/23 when it dipped to 12.5 at 2:30 pm. CYA was at 45 during this period, fyi. I think that's when (on 5/23) we thought I'd won the battle, and I was letting FC drift down. Since then, the FC was below 7 only once on 5/28 and was at 5.5 when I turned SWG back on. On 5/29, FC was 7.5 and pH was 7.6. I turned SWG back off to get FC down to 5. This morning at 10:15 am (when I noticed green algae dust), FC = 5.5, CC = 0, pH = 7.6, Ak = 80 and CYA was about 65 as I started addingCYA again on 5/29 because I thought algae was long gone.
So, did I not keep FC over 15 long enough? How long is long enough? I think I had FC over 15 for a longer period than 5/21 to 5/23 but did not have reagent until 5/21 to know FC for sure. I know that I have to have FC at 20 now that CYA is up. Other thoughts???? Love my pool, hate the algae.

Is your vinyl liner blue? If so, then I think you may have yellow/mustard algae and not green algae. Yellow+Blue(cyan) = Green. You describe the algae as "dust" which sounds more like yellow/mustard algae and would explain why the usual chlorine maintenance levels aren't keeping it away. Is the algae mostly on the wall and floor in the shady area of the pool? Yellow/mustard algae prefers shade. Do you have any removable ladders or other equipment in the pool where the algae might be hiding out inside? For plaster pools, we have people go behind light niches where they often find a lot of yellow/mustard algae if they have such an infestation, but I don't think you have pool lights (and therefore light niches) in your vinyl pool, do you? Is the algae in areas of poor water circulation?

Also, are you sure that it's algae and not pollen?

Yes, liner is blue. as i said on other thread, algae seems to disappear in the direct sun tho I think there is almost always a yellowish band of ??? algae (or a stain) where the wall and floor meet in several areas around the pool...if that makes sense. I have a ladder, not sure if it's removable as I've never tried to take it out. I have 1 pool light. How do I identify areas of poor water circulation? I'm fairly sure it's algae and not pollen.
Just read section on mustard algae, and I think you're absolutely right...that's the problem! No wonder my efforts were not enough. Sounds like a major production to get rid of mustard algae.
Many, many thanks!!!

Just realized that I posted a response on the other thread so left out some info here. CYA was about 65 on 5/30 so my shock level is now 20, correct? I'm going with the mustard algae theory so will shock at 20 till FC loss is < 1 ppm. Hoping that is done today (I was out of town all day yesterday and couldn't do much). When that's done, I'll move to super shock to get rid of mustard algae and will keep FC at or above 35 to 40 for 24 hours, correct? I've got to figure out how to get light out of pool. Can I put robotic cleaner and cloth bag, rubber mat (float) and nylon recliner floats in pool for 1 hour (in super shock) or is it better to clean with bleach solution? Also, instructions say to wash bathing suits. Do I need to use bleach with suits?