When to end SLAM

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Byeman

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May 21, 2011
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I have a question about when to end the SLAM process. CYA = ~30. Pool is ~26,500 gallons. My target SLAM Chlorine level is 13.

I know that i am near the end at present, overnight and this morning around 7:00am (after multiple "SLAMings" yesterday), FC = ~5.0, CC >0.5. Over 4 hrs later, FC down to ~3.5, CC still >0.5.

Since FC continues to drop over time, I know the process is not yet complete, but since CC is negligible, and FC is dropping (albeit at a relatively slow rate), i believe i am close to the end of the process. Do I still add enough Chlorine to take the pool to 13 one more time, which im concerned might leave the chlorine level higher than target for an extended period of time, or is there a middle Chlorine level to target?

Thanks!
 
You seem to be confusing how a pool store tells you to "shock your pool" by your comment "multiple "SLAMings" yesterday".

A SLAM Process is one continuous process, we continue to test and adjust the FC back to shock level during the SLAM Process as often as possible. In your case, with a CYA of 30 your shock level is 12 according to the [FC/CYA][/FC/CYA]

So, when to end a SLAM Process? According to the directions we only end the slam when 3 things are true:

CC is 0.5 or lower
You pass an Overnight Chlorine Loss Test(ie overnight FC loss test shows a loss of 1.0 ppm or less)
The water is clear.

So, you have CC .5, that is a pass.

Have you attempted an Overnight Chlorine Loss Test?

Is the water clear? When we say cler we mean you see no visible evidence of algae and if you toss a quarter in the deep end you not only can see the coin, but generally can see heads or tails.

There is no middle ground, you are either in a SLAM Process and you keep the FC at shock level to teh best of your ability or it has ended and you let the FC drift back down to your target.
 
Thanks for the quick response! Apologize for the semantics, but agree with your point. I also noticed I messed up my > and < signs, but fortunately you knew what i meant. My pool is a pretty blue (not so at the start of the process), so no algae, and the CC are negligible, however is did see the FC drop of 1.5 in ~4 hrs, so clearly i cannot pass the "overnight" test. That said, I believe what I'm hearing is that my SLAM process is not yet complete since the FC isn't holding for 12+ hours, and i need to add the correct amount of chlorine to take it back up to my target 13 at least one more time. Please let me know if you disagree. Thanks!
 
Byeman said:
Thanks for the quick response! Apologize for the semantics, but agree with your point. I also noticed I messed up my > and < signs, but fortunately you knew what i meant. My pool is a pretty blue (not so at the start of the process), so no algae, and the CC are negligible, however is did see the FC drop of 1.5 in ~4 hrs, so clearly i cannot pass the "overnight" test. That said, I believe what I'm hearing is that my SLAM process is not yet complete since the FC isn't holding for 12+ hours, and i need to add the correct amount of chlorine to take it back up to my target 13 at least one more time. Please let me know if you disagree. Thanks!
Click to expand...
It's not the "FC isn't holding for 12+ hours" that we are looking for.

FC loss during the day is normal and to be expected, the UV rays of the sun depletes FC.

What we are looking for is the "overnight" part, what happens when we take UV away form the pool. How does it react then. A minimal loss is to be expected overnight, every pool has some loss - that why the "pass" on an Overnight Chlorine Loss Test is 1.0 or less loss.

Keep it at shock level today, bring it back to shock level as the sun is going down and start the Overnight Chlorine Loss Test. maybe tomorrow you will be relaxing with an adult beverage looking at the water, not working on it.
 
To followup on this, last night my FC was ~10.5, CC = ~0, this morning, FC = ~10.0, CC <0.5... appears all 3 SLAM conditions have been met.

To summarize my pool opening process...
1. Removed about 2 steps of existing water and replaced with new
1.5 Added fresh DE (cleaned the filter of DE on the fall shutdown)
2. Adjusted the ph (soda ash) and checked the CYA (mine was ~35), the table suggested my target shock level to be 14
3. Added 726 oz of 6.05% Bleach
4. 1 hour later, FC ~2.5, CC ~2.5, added 605 oz of bleach
5. 1 hour later, FC ~3.0, CC ~5.0, added 484 oz of bleach (all i had, then ran to the store for more)
6. 1.5 hours later, FC ~2.5, CC ~5.0, added 605 oz of bleach
7. 1 hour later, added 484 oz bleach (didn't note the Chlorine levels)
8. 1.25 hours later, FC ~8, CC <0.5, added 242 oz bleach
9. 13 hrs later, FC ~3.5, CC <0, added 605 oz bleach
7 hours later, FC 10.5, CC 0
Overnight, FC 10, CC <0.5

In total, I used 31 - 121 oz jugs of bleach.

Next step, replace the DE in the filter (the filtering in the process has increased the pressure in the filter by 10) and be on my way.

Thanks again tim5055 for the clarification on the process.
 
Byeman said:
To followup on this, last night my FC was ~10.5, CC = ~0, this morning, FC = ~10.0, CC <0.5... appears all 3 SLAM conditions have been met.

To summarize my pool opening process...
1. Removed about 2 steps of existing water and replaced with new
1.5 Added fresh DE (cleaned the filter of DE on the fall shutdown)
2. Adjusted the ph (soda ash) and checked the CYA (mine was ~35), the table suggested my target shock level to be 14
3. Added 726 oz of 6.05% Bleach
4. 1 hour later, FC ~2.5, CC ~2.5, added 605 oz of bleach
5. 1 hour later, FC ~3.0, CC ~5.0, added 484 oz of bleach (all i had, then ran to the store for more)
6. 1.5 hours later, FC ~2.5, CC ~5.0, added 605 oz of bleach
7. 1 hour later, added 484 oz bleach (didn't note the Chlorine levels)
8. 1.25 hours later, FC ~8, CC <0.5, added 242 oz bleach
9. 13 hrs later, FC ~3.5, CC <0, added 605 oz bleach
7 hours later, FC 10.5, CC 0
Overnight, FC 10, CC <0.5

In total, I used 31 - 121 oz jugs of bleach.

Next step, replace the DE in the filter (the filtering in the process has increased the pressure in the filter by 10) and be on my way.

Thanks again tim5055 for the clarification on the process.
Click to expand...
I'm glad it helped.

Now to my next question. What is the filter pressure when it's clean? Our recommendation is to backwash/bump the filter when the pressure rises 25% above the clean pressure.
 
FYI -- you cannot measure a CYA of 35. The vial used for the test is in logarithmic scale. So when you test CYA, you always round up to the next nearest full line on the vial - so your ~35 is 40.

To mitigate that, I always fill the vial to a measurement line, say 80, glance for the dot, see it, fill to 70, glance, see it, fill to 60, obscured, call it 60.

Take care.
 
My pressure with fresh DE measures 20. It is now at 30, and my pool cleaner doesn't move quite as well as it typically does, which i assume is a function of the slightly reduced water flow from my partially blocked filter. I have found over time that simply cleaning and starting over rather than backflushing is the better way to go. I then know how much DE is in the filter, and it is fairly easy to do, so its worth the extra effort. Its common for me to change the DE and clean the filters right after getting the pool up to speed and all (or most) of the initial debris, gunk etc from the winter is removed from the pool. The now fresh filter/media typically will last most of the summer if I remember right.

mknauss, noted on the CYA comment, my reading was between 30 and 40, so i assumed 35. Didnt realize that CYA was a logarithmic scale. Good to know.
 
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