SLAM-ing question

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ScubaDoo

ScubaDoo

Well-known member
Jul 3, 2019
133
Great White North
Pool Size
80000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Zodiac LM3-24
Been SLAM-ing since the weekend after opening pool. CYA- 25, FC- 10, PH- 7.2.

Water cleared up gradually and has been very clear for a couple days now. Been getting high CC readings (1.5) the last couple days though. Which brought a chemistry question to mind: I was curious if high CC could be due to the sun killing off the chlorine during the day? Or is CC only present when it's killing off an organic?

TIA for the chemistry lesson. 😄
 
There are a few reasons for higher CCs, organics, ammonia etc.

Sun on the pool should help reduce CCs. That is why I regularly remove my cover from my mostly covered pool.
 
As long as your CC is above 0.5, you should continue the SLAM. The three criteria for finishing a SLAM are
1. Passing OCLT
2. CC of 0.5 or less
3. Water is gin clear

You've got some sort of organic material lurking in your pool. Check in light niches, behind and on the stairs and/or steps, and brush brush brush.
 
Wobblerlorri said:
As long as your CC is above 0.5, you should continue the SLAM. The three criteria for finishing a SLAM are
1. Passing OCLT
2. CC of 0.5 or less
3. Water is gin clear

You've got some sort of organic material working in your pool. Check in light niches, behind and on the stairs and/or steps, and brush brush brush.
Click to expand...
It's just very strange, the water is crystal clear, nothing ate up FC last night yet CC remains.

Can CC linger from killing all the algae at open last weekend? I've back washed three times since open so it should be clean in the filter...
 
CC is just any chemical that was combined with the chlorine. Unless you have a lot of muck and debris in the pool most are water soluble so they won't filter out. They are removed as the oxidation process proceeds and eventually gas off as CO2 and other compounds. When your pool first clears up often algae and other contaminants are broken down to soluble compounds that appear to clear up the water but they still need further reaction to completely break them down to chemicals that can gas off. SLAM levels of FC and UV light help this process along.
 
Definitely keep at it until that CC drops. Something is brewing somewhere and just hasn't been killed yet. Remove you ladder and scrub it down, if the rubber ends come up, take those off and squirt some LC inside if you can. Also, are you brushing? Sometimes dirt or pollen can build up on the walls and its good to brush it. Also, since you've got a vinyl liner, I assume you have those plastic steps and some rubber stripping between the steps and the liner? Scrub that stripping too
 
I have been scrubbing daily and the robots been going during the day. The Robot's filters are rinsing some slightly murky water out of them when I clean it out. The ladder was out of the water until yesterday and i put them in but were out all winter (shouldn't have any algae on them...) But I'll check. I will scrub the rubber trim around the steps some more. I've also found algae behind the lights before -- I scrubbed that early in the SLAM but I'll check again.

I'll keep at it.

The CYA is very low (25) -- been waiting to complete the SLAM to bring it up. Any idea if the lower CYA allows the CC to oxidize faster in the sun?
 
Your CYA is 30. There is no way to accurately measure 25 as the scale is logarithmic not linear.
For CYA 30 your SLAM level FC is 12.

SLAM Process - how closely did you follow this?
You aren't done with the SLAM Process until you pass all three criteria.
 
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proavia said:
Your CYA is 30. There is no way to accurately measure 25 as the scale is logarithmic not linear.
For CYA 30 your SLAM level FC is 12.

SLAM Process - how closely did you follow this?
You aren't done with the SLAM Process until you pass all three criteria.
Click to expand...
I don't know the algorithm but I could still see the dot at 30. Added a little bit more and could barely see it. The scale would line up with 25 or even 20. I don't have 30... Was very visible at 30.

Regarding following the SLAM procedures, I've following the steps... Not my first rodeo on the SLAM. I know it takes awhile, and I'm not doubting the process -- as per my post I just had a chemistry question re: CC.
 

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If you could see the dot at 30 and not see it at 20, your CYA is 30. Don't interpolate between the two, just round up and dose FC based on the higher CYA number.

SLAM Process is most effective with CYA between 30 and 40. If CYA below 30 you lose too much chlorine to the sun.

Since it's not your first rodeo, you already know what the three criteria are to pass the SLAM Process. Doesn't matter why you have CC even though you've met the other criteria. Keep at the SLAM Process until you meet all the criteria.
 
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Just an update, it's been a week at 12FC and the CC hasn't dropped over a week.

We've been brushing, cleaned out the lights, pool ladder and steps. Could it be organics left over in the filter? I've backwashed 5 times since opening so I wouldn't think it would be but I'm at a loss here...

Pool water is crystal clear still, I haven't tried another OCLT since the CC is still 2-4 over the last week. When I did start keeping the FC above 12 (12-14) the CC seemed to climb slightly with it (from 2 to 3-4).

Any suggestions? Am I missing something here?
 
Have you added any chemicals aside from liquid chlorine and acid? There are some non-chlorine "shock" treatments that register on the test as CCs.
 
No, been using liquid chlorine (10.8%) and supplementing with the SWG so I'm not buying liquid chlorine constantly.

I only added enough CYA to get to 30 so the FC doesn't need to be so high. I was going to raise it up after the SLAM.
 
So... This was an odd one. But I think I found the culprit of my mysterious CC values.
I
couldn't figure out how I could possibly be getting 2-3 CC values after having the FC at SLAM level for so long...

At the start of the year I bought some new DPD powder for the test kit. But was going to use up all of the remaining DPD powder I had. Sure enough, try the new powder and... CC 0. On multiple tests, and CC 0.5 with the solar cover on.

Afterwards I noticed there is a tiny best before on the DPD powder label.

I'll run a OCLT tonight and see what we have tomorrow, but I'm pretty confident that was the issue.
 
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