Slamming Help!

Apr 26, 2015
59
Leesburg, GA
I have a 20' AGP which holds roughly 8,600 gal. I'm using chlorine. This is my first season with this pool and using chlorine after having to replace a similar pool which I was using a SWG which rusted out the support beams after three seasons of use.

Cut to the chase: I am attempting to use the "slam" method for the first time.

I got algae from letting my FAC run too low. Yesterday morning water was cloudy and I vacuumed up some green residue on the bottom. I added a 121 oz jug of chlorine and one lb of cal hypo.

By afternoon water was clear with some greyish-looking residue on bottom. Apparently all the chlorine was consumed during the day by the bright sunshine and algae as I tested the water and my K-2006 kit showed the FAC was close to zero, TAC was zero, CH was 260, CYA was 40, TA was 70 and PH was 7.2. Water was clear with a small amount of residue on bottom. I let a pool store test my water and they came up with roughly the same numbers.

I upped the FAC to 16 IAW the chart I saw on this site. There was still about an hour of sunlight left in the day when I added the chlorine.

This morning, approx. 0800, after sun had been up roughly an hour, I tested some of the parameters again. My FC was 14, CC was 0.2 and ph was 7.5. Water was crystal clear with a lot of dead algae (I assume) on the bottom.

Questions: Do I up the FAC to 16 this morning or monitor it during the day and up it later? I guess I am really asking if I need to have it close to 16 this evening so that I can see if it "holds" within 1 ppm overnight or if I can do the test with it a little less than 16 if that's where it is by late afternoon?

Should I vacuum up the residue on the bottom or just sweep it and assume the high level of chlorine will take care of it? If I vacuum it I believe the fine particles will simply pass through and will remain in the water.

My thoughts are that the algae is gone because it "held" within 2 ppm overnight with maybe 3 total hours of sunlight added. Also, the water is crystal clear with a lot of "dead" stuff on the bottom. Does this seem reasonable?

What do I need to do today/tomorrow?
 
Yes, keep the FC at SLAM level until:
1. Water is clear
2. You do not lose any more than 1ppm of FC overnight (that's the OCLT)
3. CC (Combined Chlorine) is <.5
** You MUST meet ALL 3 items above to properly do a SLAM. Simply “spiking" the FC higher than normal isn't SLAMming, therefore there’s a good chance your algae will return.

Don't bother testing PH anymore during the same - it will be off.

Continue to run your pump 24/7. Remove any “muck” and debris, scrub all parts of your pool to expose any algae, and vacuum/clean (or backwash) filter as necessary. You may have to do this several times. It's a lot of babysitting, but with patience and consistency, you will succeed.

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Hope this helps to answer your question(s). If you need anything else, please let us know. Good luck, and have a great day.
 
Thanks for the quick reply. I will go ahead and up it to 16 and try to keep it there 'till evening and then do the OCLT to see where I stand by tomorrow morning. I will vacuum and brush also.

Hopefully I will have good news by morning...

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I guess my troubles began because I was not diligent enough to keep the FAC level above 3 at all times. That allowed the algae to get a foothold. I'm learning, thanks to the help and knowledge of the many fine people on this forum.
 
Success! Yesterday a.m. test revealed a loss of only 0.6 ppm overnight, clear water and CC nearly zero. I'm letting the FC drift back down to "normal" level (between 3 and 5 ppm). I will add chlorine when the level drops below 5 ppm.

During the slam, ph level is not checked. At what point do I resume testing/adjusting ph level? I'm assuming I will resume that test when FC drops to 7 ppm or thereabouts. Does that sound reasonable?

Happy Fathers day to all you fathers out there (myself included)!
 
Success! Yesterday a.m. test revealed a loss of only 0.6 ppm overnight, clear water and CC nearly zero. I'm letting the FC drift back down to "normal" level (between 3 and 5 ppm). I will add chlorine when the level drops below 5 ppm.

During the slam, ph level is not checked. At what point do I resume testing/adjusting ph level? I'm assuming I will resume that test when FC drops to 7 ppm or thereabouts. Does that sound reasonable?

Happy Fathers day to all you fathers out there (myself included)!
You got it! :goodjob:

As soon as FC drops below 10 you can go ahead and retest everything and start fine-tuning.
 
This mornings overnight test showed virtually zero drop-off of FC and there was zero residue on the bottom. Everything's looking great. Thanks a ton to all members of this forum as I'm sure it will save me a ton of time, money and effort over the years as my family enjoys our sparkling pool.

My FC measured 8 ppm, CC was < 0.5, ph was 7.4 and TA was 90. I didn't measure CYA as I assume it is still around 40 and will "hold" at that level for a while (at least 'till a significant amount of water is replaced due to splashing, rain, etc.

I plan to keep my FC level between 3 and 5 as per the chart and hopefully I will be GTG all summer.
 
Congrats Billy on passing the SLAM. :goodjob: Your numbers do in-fact look solid. So now you know to use the Chlorine/CYA chart as your primary reference to ensure your FC never drops below what is recommended for your "current" CYA. As hot as it gets in Georgia, don't risk going much lower than your target. In fact, shooting for 1-2 ppm over your target probably won't hurt. I'm sure that GA sunshine will burn it off by the end of the day. Enjoy your weekend and have a great swimming season.
 
Thanks Texas. I'll be testing a few times during the day to see how much the FC drops off each day due to the SW GA sunshine and will bump up as necessary to compensate per your recommendation.

Congrats Billy on passing the SLAM. :goodjob: Your numbers do in-fact look solid. So now you know to use the Chlorine/CYA chart as your primary reference to ensure your FC never drops below what is recommended for your "current" CYA. As hot as it gets in Georgia, don't risk going much lower than your target. In fact, shooting for 1-2 ppm over your target probably won't hurt. I'm sure that GA sunshine will burn it off by the end of the day. Enjoy your weekend and have a great swimming season.
 

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