High CC and SLAMing

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regimom88

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Apr 21, 2014
21
United States
Tested my water earlier and here's what I had:

FC: 1.5
CC: 3
pH: 7.6
TA: 120
CYA: 60

So everything looks good but the CC, right? I did some reading and saw that I need to SLAM again as something's going on. I added approximately 360 oz bleach per the pool math calculator to raise FC to shock level of 24. I waited until the sun went down, added the bleach, waited an hour and tested the water. The FC only came up to 3 but the CC went down to .5.

My water is perfectly clear so I'm a little worried what the reason for such high CC could be. Also why did the FC only come up to 3 after adding so much bleach? Do I continue SLAMing and go add more bleach?

TIA
 
Good morning Tia. True, your CC was higher than our recommended >5 or less, and your FC was very low, so you SLAMed raising to 24. Not sure "when" you did that initial dose, but if it was in the morning or mid-day, and you never added any more bleach, a lot of the FC was probably lost to sun and algae as it battled. That's why you saw the FC go down quickly as well as the CC because it was taking care of the trash in the water. Remember - to SLAM means to MAINTAIN that FC level all day & night. It can never drop below 24 during your SLAM. It is good that your CC has dropped closer to the recommended <.5. But your FC is still low. For a CYA of 60 (SWG pool), your TARGET FC should be 4, and NEVER lower than 3 on a normal day. Most importantly, remember, a SLAM is typically not a one day event. If you get by with only 2-3 days of a SLAM you are very fortunate.

Yes, keep the SLAM level of 24 through today and do an overnight FC loss test (OCLT). Make sure you pass all 3 SLAM requirements tomorrow morning as follows:
1. Water is clear
2. You do not lose any more than 1ppm of FC overnight (that's the OCLT); make sure you do the starting and ending FC comparisons when the sun is down.
3. CC (Combined Chlorine) is <.5

After the SLAM, also suggest you bump your CYA up slightly to about 70 as noted on the Chlorine/CYA chart (link below) for your SWG system. Hope this helps. Good luck!
 
Hi regimom88, whatever the cause you will need to add more chlorine. It was likely either old weak bleach, or something was eating it quickly. Add the same amount and see what reading you get. If it holds then keep SLAMming, if not then get new bleach? are these readings a recent development? were the numbers good last week? what led up to this?

edit: i see you started a thread 3 weeks ago about slamming, so your bleach must be fresh. was the SLAM completed successfully meeting all 3 criteria, it didnt say in your thread. likely you need to start SLAM over to completion
 
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