Chlorine went down to 0 - must I shock?

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mknauss said:
Keep your FC at shock level based on your CYA until you pass the three criteria as shown in the SLAM article. Pool School - SLAM - Shock Level And Maintain
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Sorry - just noticed the line that says "When all three are true, you are done SLAMing and can allow the FC to drift down to normal levels." So of course you are right obv. i have to keep it up high until it passes the OCLT. Doh!

I just redid the CYA test with my back to the sun. It is super sunny out today and I could see the dot at least a little until almost the whole tube was full - about 35?!? Now I'm not sure what to think it is.
 
The CYA test result is greatly affected by the conditions in which you do the test. So today it was sunny and you did the test under the proper conditions.

I use the 'glance' method taught by KimKats.
You fill the vial to a line, say 90, glance, if you see the dot, fill to 80, glance, etc until you did not see the dot with a GLANCE. If you stare, you will see that dot to the top!

Adjust your shock FC if you are confident your CYA is lower. Remember, the only way CYA leaves the pool in a significant amount is by draining water and replacing it with fresh water.

Take care.
 
OK I definitely stared. I just tried again using the glance method. At 60 I could still just barely see the dot. At 55, at a glance it wasn't there. I had enough mixture in the bottle to do it twice, and got the same result both times.

I do have some extra Cyanuric Acid - should I add more to bring it to 70 or lower my shock level to 22?

Thanks so much for all your help!!!

That was the last of my R-0013 for the CYA test. Will have to order more.
 
Always round up. So use 60 for your CYA. Shock is 24 FC.

Not much change, actually within the error range of all CYA tests (+/-10ppm)

Good job.
 
turbowop said:
While you're at it order the 50ppm CYA standard. That way you have a direct comparison as to how the dot should look. Helped me out for sure.
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OK my google-fu is not helping to much. Seems to be a dearth of information about this. I found this super old thread:
CYA 50ppm Standard results

And this is the product you're referring to?
CYA Standard, 50ppm, 30mL Clear Choice Labs

I feel like this CYA test is kind of like when you get eyeglasses and the optometrist says, "which is better, this one or this one?" and they all look the same! Considering how controversial the safety of Cyanuric Acid is, I sure wish there was a better test though I'm certainly no chemist to understand it all.
 
The shock is still not maintaining. Every day we bring it up to 24, then by evening it is back to 15. We bring it up to 24 again, by morning it is 16. This is crazy!! What could be causing this? I do not like swimming in a bath of bleach. :-(
 

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Aubade said:
The shock is still not maintaining. Every day we bring it up to 24, then by evening it is back to 15. We bring it up to 24 again, by morning it is 16. This is crazy!! What could be causing this? I do not like swimming in a bath of bleach. :-(
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Your FC is consumed by two things, UV from the sun and organics. Nothing else.

Remember, the chlorine in your pool at shock level with a CYA of 60 has less active chlorine than most tap water in the United States.

Take care.
 
Aubade said:
The shock is still not maintaining. Every day we bring it up to 24, then by evening it is back to 15. We bring it up to 24 again, by morning it is 16. This is crazy!! What could be causing this? I do not like swimming in a bath of bleach. :-(
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That is to be expected. The higher the FC, the faster the sun depletes it. That is why we advocate the SLAM -- shock level and maintain - and not a one-time megadose of chlorine - a pool-store "shock".

If something is growing in the water, it will use up some FC as it dies. Then when the FC dips below some level, it starts growing again, which depletes even more FC. So they key to winning the fight is to keep hitting. This is a death match with algae. Don't knock it down and then let it recover and get back up. Knock it down and kick it while it's on the mat until it's dead. Frequent testing and replenishment. You might actually be done with the SLAM, but you won;t know it unless you can determine that the overnight loss was next to nothing.

You've had a few days practice so now what you read should make more sense. Study the SLAM Process and follow them.
 
Aubade said:
Then of course we got a ton of rain which no doubt will mess up the readings. *sigh*
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Rainfall does not appreciably effect pool water chemistry. Unless of course it is of Ark building proportions or a flood.

pH may rise due to the aeration. Any FC loss is from organics blown into the pool.

Take care.
 
JoeSelf said:
If you have a light, did you pull it out and check behind it?
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We do have a couple lights but i have no idea how to get them out.

It's been 3 days now (wed, thur, fri) my husband checked at noon & 4 pm (in addition to our 8am and 8pm tests). Every. Single. Time. we add more chlorine to get it to 24, then at the next reading it is down to 16ish.

I don't understand what the problem could be. The pool was never cloudy, not even when we started this. It is sparkling clear. The CC has been 0 for days. We've cleaned all the filters, everything seems good. Could the fact it can't hold the high level of chlorine just be due to it being in a very sunny spot? There is basically no shade on our pool, and it isn't that deep. (3' low end to just over 5' deep).
 
The even weirder thing is we opened the pool early this year in April. It was our first full season. We didn't add new CYA, having read that it stays in the water (and didn't test it either). We also didn't realize that you basically have to run the filter 24-7 in the height of pollen. We had the solar cover on and one night I looked under it to find an absolute cloudy yellow mess! I'm still not totally sure whether it was just pollen or mustard algae, but it seemed like both based on the fact that the brownish stains were clinging to the sides of the pool, especially in shadier spots.

At that point I did a full test including the CYA and realized it was 0, so I used pool calculator to add enough to get it to 70. (which I don't understand how it got so low knowing it was good last summer when the pool was brand new, and fiberglass pools don't get totally drained over the winter). Then I followed the instructions here and brought it up to the mustard algae level shock, soaked anything that had touched the water (pool toys, skimmer), etc. In about a week it cleared up and passed the OCLT. This was late April/early May and everything has been great since. Not a spot of cloudiness - sparkling clear just with the SWCG.

So how could the SLAM have gone so well in the spring but not be working now?
 
Have you looked at your filter media? It might be filtering the algae out but be filled with it. If you dont kill all of the algae it will come back.
 
Aubade said:
Could the fact it can't hold the high level of chlorine just be due to it being in a very sunny spot? There is basically no shade on our pool, and it isn't that deep. (3' low end to just over 5' deep).
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For the reason you mention, this is why the OCLT is done at night. It removes all influence of the Sun's UV. Since there is no UV at night, any chlorine loss is due to "stuff" within the pool water.

FC loss during the day is expected, usually 2-4ppm depending on pool specific conditions.
 

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