Chlorine is disappearing!

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Yep, something's in the water. I suspect that your SWG is just keeping up to suppress the algae from turning everything green. Check hidden spots like behind pool lights, skimmer weir door, etc. Dark locations like the filter are less likely to harbour algae.

The more you stay on top with maintaining slam FC, the faster you'll be done.

I would leave the pool cover off during the slam so the pool can breathe, and get some UV to get rid of CC, if there is any. Have you tested CC?

It would also be better to add new information as a new post, rather than adding it to an existing one via edit.

The edit feature is great to correct something in an existing post, especially to make sure that future readers don't take the wrong message from a statement that turned out to be wrong.

But "edit" doesn't notify followers of a thread that there is new information, or boost its position in the forum list, and you might never get a reply. I just went back here to check if I missed updates because you posted in another thread that you failed the OCLT and started to SLAM.
 
mgtfp said:
The 7 was just for the OCLT - now the fun begins...
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Indeed!

Yesterday my CYA reading was around 45 to 50.
Just tested earlier today to confirm SLAM levels & it was reading 70! Didn't add any CYA so that's an interesting change. And I quickly lobbed into the pool shop with a sample and they confirmed with a similar reading (they say 65). I needed a new drum of CL anyway.
So SLAM level is 28. And here we go...

Just on the CYA level, I dosed fairly high yesterday (not quite SLAM levels but definitely between 5 to 8 ppm) so left field idea...I wonder if I had some ammonia producing bacteria making my CYA drop & with yesterdays effort have killed it off some? And just to repeat, pool is 2 years old and I have always had to top up CYA as a weekly dose. Maybe 0.25 to 0.5 cup per week of the powder. That'd keep it around to 40 mark +- 10, so between 30 to 50.
Just an idea & likely I will never know. Let's concentrate on the SLAM for now.
 
AlexPowell said:
If CYA and Chlorine are both being lost - could it be that there is a lot of Ammonia in the pool?
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That's a possibility. I think it might be too late to test now as if there was any bacteria producing ammonia, the bacteria is getting killed off during the SLAM.
I had never known that topping up CYA levels weekly or fortnightly was unusual - to me it's always been normal since getting the pool built 2 years ago. It's only now during these forum discussions (and another forum) that I realise it's an issue.

Next question in this battle...I'm running out of chlorine titrating reagent so it was suggested elsewhere to dilute pool water 50:50 with demineralized water. Then test as normal but each drop is 1ppm, no need for the division by 2. It sounds valid to me. Opinions? Anyway, until I get my delivery of more reagent I'll keep going with the dilution 50:50. I'm using a medicine cup to ensure I get exact 50:50 of each.
 
Youfah Mizzum said:
That's a possibility. I think it might be too late to test now as if there was any bacteria producing ammonia, the bacteria is getting killed off during the SLAM.
I had never known that topping up CYA levels weekly or fortnightly was unusual - to me it's always been normal since getting the pool built 2 years ago. It's only now during these forum discussions (and another forum) that I realise it's an issue.

Next question in this battle...I'm running out of chlorine titrating reagent so it was suggested elsewhere to dilute pool water 50:50 with demineralized water. Then test as normal but each drop is 1ppm, no need for the division by 2. It sounds valid to me. Opinions? Anyway, until I get my delivery of more reagent I'll keep going with the dilution 50:50. I'm using a medicine cup to ensure I get exact 50:50 of each.
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Or you can just use a 5ml sample & each drop equals 1ppm , much simpler.

For a successful SLAM Process
you need to continue to MAINTAIN Slam level fc for your cya as often as possible until you meet ALL 3 end of slam criteria-

You are done when:

CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
the water is clear.
(Crystal Clear w/no algae dead or alive)

*Check & scrub every nook & cranny where algae may hide (light niches, steps, drain covers, ladder handrails, skimmer throats/weirs, etc.)
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.

SLAM ON 👍🏻
 
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Seems PoolMath got it wrong somehow. For a CYA at 70, it suggested 5 litres of bleach (12.5%) to get from 0 to 28 ppm. Even 1 to 28 needs 4.9 litres so close enough.

Now when I test my chlorine I'm getting 36 ppm. Looks like I overshot the mark! Doesn't matter I guess - better too much than not enough & it also preserves my reagent because now I can just let it burn off over the day & test at dusk for tonights OCLT.
 
Youfah Mizzum said:
Seems PoolMath got it wrong somehow. For a CYA at 70, it suggested 5 litres of bleach (12.5%) to get from 0 to 28 ppm. Even 1 to 28 needs 4.9 litres so close enough.

Now when I test my chlorine I'm getting 36 ppm. Looks like I overshot the mark! Doesn't matter I guess - better too much than not enough & it also preserves my reagent because now I can just let it burn off over the day & test at dusk for tonights OCLT.
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Keep pushing the chlorine back up to 28 every few hours. Testing it and dosing once a day it going to make it take forever. It would be better not to go above SLAM level as it just wastes chlorine.
 

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You're going to struggle even with slam because the so called yo-yo you have going on with the CYA is at times not enough to stabilize the chlorine so you'll be burning through chlorine just from the UV effect. I'm not buying into the ammonia theory because ammonia will take it all the way and not yo-yo the level up and down. Once it's eliminated your done and don't have to worry and can be well on the way with slam. I still believe this is op error.
 
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Bperry said:
Keep pushing the chlorine back up to 28 every few hours. Testing it and dosing once a day it going to make it take forever. It would be better not to go above SLAM level as it just wastes chlorine.
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Yeah I get that. But it's well in excess of 28. I wouldn't have gone above SLAM level if PoolMath gave me the correct quantity to add! It said 5 L so that's what I did. I'm betting that my evening OCLT test it will still be above 28.

wireform said:
I'm not buying the ammonia theory....I still believe this is op error
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Re ammonia, I have no other explanation for the requirement to be adding CYA.

I'd agree about op error except I've been testing CYA for 2 years so I kinda know what I'm doing (I like to think). I guarantee that CYA drops week by week. And I know we don't like pool shop tests here, but their testing concurs with mine +/- 5. Anyway, I tested CYA twice this morning and at 70ppm the black logo at the bottom of the vial was barely visible. My bet it was between 65 and 70 which matched the shop test. Until now I didn't realise it was abnormal to require a little dose of CYA each week.

I'll retest CYA tomorrow morning after the OCLT and redose with chlorine - maybe 100-200 ml less than PoolMath says as it overdosed me this morning.
 
aussieta said:
how are you adding your cya
how are you performing the cya test
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Sprinkling powder directly into the pool and/or skimmer box.
It's actually nice to know its up around 70. I don't think I've ever had it so high. But yeah, SLAMming will take more chlorine. Oh well, I wasn't to know it would increase unexpectedly. Last test before this mornings was yesterday morning & I didn't add more CYA. Test showed about 45 so overnight it's shot up to 70.

Doing CYA test according to CCL instructions:
  1. Rinse the CYA mixing tube with pool water.
  2. Fill the CYA mixing tube with pool water to the mark indicated. Allow the water to come to room temperature if pool is cold.
  3. Fill the CYA mixing tube to the mark indicated with CYA Detection Reagent.
  4. Mix the CYA mixing tube thoroughly for 30 seconds.
  5. Hold the CYA viewing tube at waist level and, looking down into the tube, slowly pour the contents of the mixing tube in until the logo at the base of the tube disappears.
 
Youfah Mizzum said:
Sprinkling powder directly into the pool and/or skimmer box.
It's actually nice to know its up around 70. I don't think I've ever had it so high. But yeah, SLAMming will take more chlorine. Oh well, I wasn't to know it would increase unexpectedly. Last test before this mornings was yesterday morning & I didn't add more CYA. Test showed about 45 so overnight it's shot up to 70.

Doing CYA test according to CCL instructions:
  1. Rinse the CYA mixing tube with pool water.
  2. Fill the CYA mixing tube with pool water to the mark indicated. Allow the water to come to room temperature if pool is cold.
  3. Fill the CYA mixing tube to the mark indicated with CYA Detection Reagent.
  4. Mix the CYA mixing tube thoroughly for 30 seconds.
  5. Hold the CYA viewing tube at waist level and, looking down into the tube, slowly pour the contents of the mixing tube in until the logo at the base of the tube disappears.
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ok, i see some room for improvement
if you add stabilizer to the skimmer, it can then be trapped and lost to backwashing
sprinkling in the pool can bleach/stain the liner as it is acidic
best to place in an old sock and hang in front of return jet, not allowing to touch the side
to test cya
up to step 4 is good
then mid morning or late afternoon
with back to the sun
fill testing tube to 100 mark
hold tube at waist level, and have a quick glance, no more than 2-3 seconds
if you see black dot, fill testing tube to 90 mark and repeat
when you cant see the black dot in a quick glance
place solution back into mixing tube
and then retest once more
if you get the same number all good
if not repeat and take an average
 
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My recommendation is if the CYA is down why bring it back up if you're slamming. Keep it lower rather then higher for the benefit of saving chlorine. As long as the slam FC is in line per the CYA level the slam will be just fine.
 
wireform said:
My recommendation is if the CYA is down why bring it back up if you're slamming.
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I didn't!!! I tested and it showed CYA at 40 to 45. Yesterday.
Then next morning (early today) I tested CYA just prior to SLAMming to get correct qty of chlorine to add. And bingo, it showed 70.

I didn't add anything!

Aussieta - OK. I wont put CYA into skimmer box. Its a powder so should dissolve and dissipate through the water anyway if it gets stuck in the filter.
The CYA test - I am doing it already pretty much as you say. I am following the CCL guide as already stated. Just didn't think I needed to go into the exact minutae of how I do the test but what you've said is basically it.
 
Youfah Mizzum said:
I didn't!!! I tested and it showed CYA at 40 to 45. Yesterday.
Then next morning (early today) I tested CYA just prior to SLAMming to get correct qty of chlorine to add. And bingo, it showed 70.

I didn't add anything!

Aussieta - OK. I wont put CYA into skimmer box. Its a powder so should dissolve and dissipate through the water anyway if it gets stuck in the filter.
The CYA test - I am doing it already pretty much as you say. I am following the CCL guide as already stated. Just didn't think I needed to go into the exact minutae of how I do the test but what you've said is basically it.
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cya cannot go from 40-70 without adding stabilizer so must be user error
either not allowing a few days after addition of stabilizer to retest
or testing error
cya is the hardest test to get consistent results
which is why i have included the time of day
to ensure you are in shadow
 

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