Too much bleach for estimate gallons of my pool

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Catherineb

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May 22, 2013
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Hello - I'm back again. I seem to be losing a high amount of FC during the day (it's 100 degrees in Dallas) and I know a 3-4ppm loss seems to be acceptable. But I also failing the OCLT test. Last night at 11pm FC was 12.5 this morning at 6:45am it was 10. I guess it is time to slam my pool which I have already started.

Here are my test results from 5:30pm this evening:

FC 5
CC 0
PH 7.2 lowered from 7.6 to start the slam process
TA 70
CH 325
CYA 35

The pool calculator told me to add 163 oz of 8.25% bleach which I did at 9pm to begin the slam. I have just checked again and now my FC is 16.5. It has actually gone up more than what the calculator advised. I am shocking to 14 with a cya of 35.

I think the problem is I do not know the exact amount of gallons in my pool. My pool is a kidney shape. The measurements are 14.6 wide, 27ft long with a depth of 3'6, 5 and 4ft. I've tried using various methods to try and confirm my gallons are around the 12, mark but it's hard because of the kidney shape and a beach entrance.

There are no signs of algae. Pool is in the sun most of the day. Water is clear. Looks good but I am failing the OCLT test.

I know the slam process which I have started but I was hoping you could check my measurements and see if you agree on approx. 12,000 gallons for my pool. I seem to be over shooting on the bleach?

Thanks for any advice.
 
How does your water look ? I'm not that good at calc volume. Somebody else can help with that.

You can bumb your CYA up alittle to help with the FC loss due to the heat and sun.




Sent from my iPhone using Tapatalk.
 
Thanks Pwrstrk - I thought perhaps I would hold off on bumping up my CYA so that I won't need to slam using more bleach at the higher cya level but I guess it may help keep my FC during the day. Umm.
 
Catherineb said:
Thanks Pwrstrk - I thought perhaps I would hold off on bumping up my CYA so that I won't need to slam using more bleach at the higher cya level but I guess it may help keep my FC during the day. Umm.
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I would hold off on adding the extra CYA until after you complete the SLAM process.

Getting exact gallons is pretty hard to figure, as you already know. Perhaps it is closer to 10K. If I use only the FC increase (from 5 to 16.5 w/163 ozs. 8.25%), I (along w/the calc) get about 10K gallons. Guestimate.

Also, you could have picked up some very fresh bleach! It starts out higher % so that it is good when it gets to the consumer.
 
imwarren said:
Op states clear
Being over 2 ppm isn't to far off with testing error water level flucuation chlorine strength flucuation just moniter and adjust future additions
Click to expand...

Whoops missed she stated clear. That's why I was thinking if she even needed to slam.


Sent from my iPhone using Tapatalk.
 
Thanks everyone for responding.

Last night FC 16.5
This morning 14.

Yes Butterfly, I think my pool must be less that 12,000 but not sure as small as 10,000. Oh well, I will continue with the SLAM today as I do not have far to go (hopefully). I will higher my CYA after the slam or perhaps 35 is ok?

As this morning's read is at 14, this is my shock rate, I will keep topping up through the day.

Thank you
 
When you added the acid to lower the pH, did it drop the amount you thought it would? Do you have before and after TA readings? You could compare the calculated Effects of Adding Chemicals in the pool calculator and double check to see if the volume worked that time, or if you overshoot there, too.

If you didn't recheck pH after adding acid, don't bother now, as the FC is too high to get an accurate reading.
 

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Thanks Richard. Yes I do have the before results.

PH was 7.6 added 23oz of acid to lower to 7.2 (yes, it did lower it to 7.2)
TA was 90 after a couple of hours it fell to 70.

I did enter the amount of acid in the pool calc before I added it to see how it would affect the TA. It said the TA would lower by 7.2 but in fact it lowered by 20. So where am I off? it must be a smaller amount of gallons in my pool.
 
Catherineb said:
Thanks Richard. Yes I do have the before results.

PH was 7.6 added 23oz of acid to lower to 7.2 (yes, it did lower it to 7.2)
TA was 90 after a couple of hours it fell to 70.

I did enter the amount of acid in the pool calc before I added it to see how it would affect the TA. It said the TA would lower by 7.2 but in fact it lowered by 20. So where am I off? it must be a smaller amount of gallons in my pool.
Click to expand...
I don't think you'd have lost 20 TA without a much larger pH drop - there's a certain amount of error in the test. But certainly more than 7. And that does tend to support the hypothesis that your pool is smaller than 12000 gallons.
 
I plugged your test results into the pool calculator using 12K as pool volume and it showed you needed 158 ounces to raise FC from 5 to 14ppm. Make sure you update all your test results in the pool calculator if anything has changed. Although you did overshoot the FC it wasn't by much.

As far as your OCLT goes, be sure you are testing when there is no sunlight on the pool. 11:00pm was full dark, and 6:45 am the sun is already up, so it is possible you lost some FC during sunrise.

I am curious as to what prompted the slam in the first place. Was it due to a past algae bloom, or just the amount of FC lost during the day? Regardless of the cause, be sure and brush the sides and floor of the pool while at shock level to expose any unseen algae to the chlorine.
 
Richard320 said:
Catherineb said:
Thanks Richard. Yes I do have the before results.

PH was 7.6 added 23oz of acid to lower to 7.2 (yes, it did lower it to 7.2)
TA was 90 after a couple of hours it fell to 70.

I did enter the amount of acid in the pool calc before I added it to see how it would affect the TA. It said the TA would lower by 7.2 but in fact it lowered by 20. So where am I off? it must be a smaller amount of gallons in my pool.
Click to expand...
I don't think you'd have lost 20 TA without a much larger pH drop - there's a certain amount of error in the test. But certainly more than 7. And that does tend to support the hypothesis that your pool is smaller than 12000 gallons.
Click to expand...

I think I should change my pool size to 11,000 for now and work off that number when adding chemicals. And see how I go with that. Thanks.
 
Catherineb said:
Richard320 said:
Catherineb said:
Thanks Richard. Yes I do have the before results.

PH was 7.6 added 23oz of acid to lower to 7.2 (yes, it did lower it to 7.2)
TA was 90 after a couple of hours it fell to 70.

I did enter the amount of acid in the pool calc before I added it to see how it would affect the TA. It said the TA would lower by 7.2 but in fact it lowered by 20. So where am I off? it must be a smaller amount of gallons in my pool.
Click to expand...
I don't think you'd have lost 20 TA without a much larger pH drop - there's a certain amount of error in the test. But certainly more than 7. And that does tend to support the hypothesis that your pool is smaller than 12000 gallons.
Click to expand...

I think I should change my pool size to 11,000 for now and work off that number when adding chemicals. And see how I go with that. Thanks.
Click to expand...
Do it in steps, since the pH change did work. Maybe 11,500 and go up or down from there.

I had it easy - I had really high TA way back when and I was able to use that to gauge the results. It only took me about a week to dial things in exactly. You'll know by the end of summer.
 
zea3 said:
I plugged your test results into the pool calculator using 12K as pool volume and it showed you needed 158 ounces to raise FC from 5 to 14ppm. Make sure you update all your test results in the pool calculator if anything has changed. Although you did overshoot the FC it wasn't by much.

As far as your OCLT goes, be sure you are testing when there is no sunlight on the pool. 11:00pm was full dark, and 6:45 am the sun is already up, so it is possible you lost some FC during sunrise.

I am curious as to what prompted the slam in the first place. Was it due to a past algae bloom, or just the amount of FC lost during the day? Regardless of the cause, be sure and brush the sides and floor of the pool while at shock level to expose any unseen algae to the chlorine.
Click to expand...

Hello Zea,
I often wonder this. Is it better to test at 11pm when it is dark and do the sample test in the house? or is it ok to take the test at 8pm while it is still light but with no sun. And I test in the morning around 8am before the sun hits the pool. Is that ok or should I get up at 6am to test? just want to be sure.

I started the slam process because I was losing 2-3ppm during the night.

Thanks
 
I don't think we have specifically defined what the sun being off the pool really means. I try to do the OCLT when it is dark or at dusk and dawn in about 1/2 light so I am comparing apples to apples so to speak. I run all my tests indoors except for the CYA test.
 
zea3 said:
I don't think we have specifically defined what the sun being off the pool really means. I try to do the OCLT when it is dark or at dusk and dawn in about 1/2 light so I am comparing apples to apples so to speak. I run all my tests indoors except for the CYA test.
Click to expand...

Yeah, I think it makes more sense to do my last test at say 11pm when it is dark and set my alarm for maybe 6am in the morning to retest. I have tested both ways and I am still not passing the OCLT. I will see how I go tonight. Thank you.
 
Richard320 said:
Have you seen this thread? It might be something to consider. think-i-may-have-found-my-fc-demand-issue-t65957.html
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It's funny you mention this. My pool light stopped working a couple of months back. I had an electrician take a look. While he wanted to charge me $875 for a new light :grrrr: which I declined, there did not seem to be a lot of gunk in there? although there was algae around the edges which I cleaned off, but this was a few weeks back so I don't think it is that. Very interesting though and thanks for sending :)
 

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