In middle of SLAM - questions

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atx78704pool

Active member
Nov 25, 2023
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Austin, TX
First SLAM - questions

My pool was clear to start this process and no visible algae, but I’m losing chlorine overnight daily so doing a SLAM to fix that issue. I didn’t think it would take much to complete this process given how good the pool has looked to this point, but my overnight loss is still much higher than I would have expected. I started this yesterday morning - below are my details up to this point. I’ve used a lot of gallons so far and o have none left (I bought double like the directions said) - is that expected? Should I be getting more at this point?

9/1 11am: added 454oz liquid chlorine

FC 0.5
Ph 7.3
TA 80
CYA 55

1pm: added 137oz

FC 15.5

5pm: added 179oz

FC: 13.5

7pm:

FC 17
CC 0.5

9/2 715am: added 327oz

FC 6.5
CC 1.0

11am : added 128oz
FC 16.5
CC 1.0

I’m gonna need to buy more chlorine at this but before I do it, I want to make sure I’m not missing something. Should I be concerned about phosphates at all? Don’t have a test kit for that if so…
 
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If I am reading this correctly, your 7pm test had FC at 17ppm and at 7:15am the FC was 6.5ppm. so this is a big drop overnight which indicates algae is still present. Have you removed or cleaned any ladders? No pool toys should be floating in the pool - remove and clean them Do not use a cover when doing a SLAM.
Furthermore, the FC for a SLAM is is 40% of the CYA level. Round up CYA to the next decade level, therefore are you really even getting to 24ppm? The best way to test that initially is to Test for FC, add LC to reach to 24ppm, circulate for 30 mins then test again to ensure you reached 24ppm. Sometimes the pool volume is off and then it is not calculating the right dosage.
The better you MAINTAIN (the M in SLAM) the FC at 24ppm the quicker the process moves along.

EDIT - Initially with a SLAM you should test every 2-3 hrs, then top FC back to SLAM level. I see you are waiting 4 hrs and you may need to do more often just to confirm you are getting to the 24ppm level.
 
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Your CYA is somewhere between 50 and 60 - so round up to 60.
SLAM Process level for a CYA of 60 is FC 24.

Have you tested FC 30 minutes after adding to see if you get to FC 24?
 
atx78704pool said:
So more chlorine is needed than what I’ve been putting on? Has the process been pointless so far if that is the case?
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Not exactly pointless but not really biting the bullet either. You need to put in what pool math says you need for the FC24. Then wait 15 minutes and check. If it hasn't reached keep adding till you have reached it once. The next time you check add per pool math to get it back to the 24 .
 

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Basically the very beginning of slam you need to rinse and repeat till you've reached the intended FC. After that just use pool math to bring it back to that number and checking at that point is unnecessary.
 
wireform said:
Noone can honestly tell you if 6 gallons are enough but that would be my wish for you.
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So at 11am when I used last bit of chlorine, FC was at 23.

I’ve since gotten more chlorine and been getting it up to 24 and testing again every 30 minutes and adding to get it back up. This is the results of each of those:

330 FC 16.5
4 FC 23
430 FC 22

It’s been cloudy all day so I do t think sun is burning much off, but not sure. Does this seem expected and I should keep doing this every 30 minutes till it holds?
 
wireform said:
Basically the very beginning of slam you need to rinse and repeat till you've reached the intended FC. After that just use pool math to bring it back to that number and checking at that point is unnecessary.
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How often at the beginning so I need to be brining it back to SLAM? If you look at my post above, I’m checking every 30 currently and it’s dropping still.
 
I think, with the last two test results, you can revert to 2 hour testing. Do test, add chlorine, wait two hours, test again. I would not continue to test after 30 minutes, you will run out of reagent quickly.

Post pictures of the pool, so we can see everything.

Are you scrubbing?
 
Ok - will do another here in a bit. It did hold on the last one I do so that’s good.

Yes, been scrubbing. Pic attached. Pool has been clear since the start - I’m more trying to rid issue of overnight chlorine loss and not a cloudy pool or anything.
 

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post a pic of the whole pool.

Do you have a main drain? Remove the cover and scrub it and in the drain.
Scrub the skimmers.
Check the weir doors for algae.
Do you have an autocover?
 
PoolStored said:
post a pic of the whole pool.

Do you have a main drain? Remove the cover and scrub it and in the drain.
Scrub the skimmers.
Check the weir doors for algae.
Do you have an autocover?
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Full pic attached.

No main drain I’m aware of. Pic of equipment also attached.
Skimmers I’ve cleaned - but will do again more thoroughly.
Noted on doors.
No auto cover.

Latest reading after 2 hours and lost 4 on my chlorine still. Added more and will check again in morning.
 

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