Minding my CSI, but still scaling in SWG

KurtinTUS

Silver Supporter
Jul 20, 2017
67
Tucson
I have been battling increased scaling this season (our second summer with a new-build pool) despite my attempts to manage the CSI. This is what the SWG looked like in early Sept after cleaning:

IMG_4497.JPG

...and this is what I have today:

IMG_4712.JPG

This is pretty representative of where I have been chemistry-wise since mid-summer:

IMG_4713.PNG

As a desert rat, I know my water is getting harder by the day, but even with my current CH, I would have thought the SWG scaling would be manageable if I kept the CSI slightly negative (which I have been trying very hard to stay on top of). Clearly, I am still doing something wrong. Any thoughts?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Kurt, I wouldn't say you are doing things wrong. In fact, if your testing is accurate and the CSI is slightly negative consistently throughout the year, you seem to be using all of your tools (Poolmath APP, testing, etc) correctly. :goodjob: But as we know, your are in a hard water environment. Imagine what your cell would look like if you didn't maintain that lower CSI? Curious, are you seeing any other signs of scale around the pool or spa?
 

KurtinTUS

Silver Supporter
Jul 20, 2017
67
Tucson
Pat, I've had some slight scaling around the pool, mostly near the skimmers. Which is all the more reason why the SWG scaling seems odd to me. Should I just run an even lower CSI and pH by adding more acid?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Should I just run an even lower CSI and pH by adding more acid?
Based on what you're seeing in the cell and around the pool, it wouldn't hurt to try maintaining the CSI at about -0.3 for a few weeks. Perhaps that's a more ideal number/range for your calcium-saturated water. If so, the scale on the SWG should slowly disintegrate. Scale around the pool may need some TLC (elbow grease), but I'd try to keep that CSI consistent for a while and watch for any signs of improvement.
 

Saturn94

Well-known member
Mar 11, 2015
1,027
SE Virginia
I understand the environment inside the cell is a bit different (higher pH) when generating chlorine. Could it be that the CSI inside the cell when generating is going into the positive?

I realize this doesn’t address any scaling in the pool.
 

KurtinTUS

Silver Supporter
Jul 20, 2017
67
Tucson
I understand the environment inside the cell is a bit different (higher pH) when generating chlorine. Could it be that the CSI inside the cell when generating is going into the positive?

I realize this doesn’t address any scaling in the pool.
That could be, because my scaling in the SWG seems much worse than the pool.
 

Leebo

Admin
TFP Expert
LifeTime Supporter
Jul 21, 2011
10,077
Eastern Ohio
Please note that I don’t have much experience with hard water plus I manually add chlorine, so I maybe off on parts of this comment.

You may wanna read up more on the topic of borates as they may help you out somewhat. Inside of your cell the chemistry does get altered a fair bit. Commonly your pH jumps out which likely puts your CSI into the positive area. Adding borates may help stabilize that pH jump and keep your CSI in the negative.
 

AUSpool

Bronze Supporter
LifeTime Supporter
TFP Guide
Sep 23, 2015
754
Brisbane, Australia.
I’ve read that due to evaporation, scale can still occur at the water surface even when your CSI negative. I believe your SWG is self cleaning but your CH is high. Your doing everything right, low CSI and pH at the lower end both help limit scale. That amount of scale over the time frame is not excessive but I would keep an eye on it just in case the self cleaning function is failing. I managed a pool with a non self cleaning SWG and it would look way worse than that, I almost expected flow to be impeded, and yet it still kept up with FC maintainance.
 

ping

TFP Expert
LifeTime Supporter
Jun 24, 2011
3,134
Long Beach, CA
How high do you let the pH get when you add acid?

Borates will help this condition as they will limit how high the pH can get inside the cell. This is one pool that I would add borates to if it were mine. Before adding borates I would drain and replace a good portion of the water to lower the CH.
 

KurtinTUS

Silver Supporter
Jul 20, 2017
67
Tucson
Appreciate all the info! I'm not ready to go with borates just yet, but will try a lower CSI via more acid for the next month or so and see if that helps the SWG scaling.
 

Demegrad9

Well-known member
May 27, 2017
362
Coventry, CT
How do you set your SWG and pump to run?

Not saying I know anything about this, but I'm curious about this pH rise caused by the cell while the cell is producing chlorine. If that is so, I wonder if running at say 25% for 24 hours per day would be different than running the cell 50% for 12 hours per day in terms of scaling.

For instance, if pH rises in the cell while it's on, this would push the CSI of the water in the cell above 0. And if the cell is constantly running, even at low percentage, the scaling would just constantly accumulate. But if you have a equal time where the cell isn't running, then your negative CSI water is just running through the cell slowly removing any scale that accumulated while the cell was previously on.

this is just a thought, could be complete non-sense.
 

KurtinTUS

Silver Supporter
Jul 20, 2017
67
Tucson
That is an interesting theory. I have been running the SWG for 20 hrs/day. Maybe less run time on a higher % would help the scaling?

Though one problem I foresee is that I've been in the 'keep the pump running nearly 24/7' camp as a way to promote general pool health & well being. If I wanted to still keep the pump running most of the 24 hr day, but with the SWG off, I will have to get smarter on programming my EasyTouch. :scratch:
 
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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
20,474
Northern NJ
If that is so, I wonder if running at say 25% for 24 hours per day would be different than running the cell 50% for 12 hours per day in terms of scaling.
The SWG generating cycle time varies with the manufacturer. For @KurtinTUS Pentiar IntelliChlor it uses 5 minute cycles.

25% would generate chlorine for 75 seconds in every 5 minutes.

50% would generate chlorine for 150 seconds in every 5 minutes.

Running the SWG for 24 hours would run for 288 generating periods a day. Running for 12 hours would would run for 144 generating periods a day.

The internal cell scaling is cumulative and I don't think varying the generating cycle will make any difference.

The InetlliChlor SWG cell has a self-cleaning cycle which reverses the cell polarity, reducing calcium buildup. This feature turns the cell on and off at regular intervals to minimize calcium and scale buildup and further maximizes cell life

For the first thirty (30) days of cell operation, the self-cleaning cycle, is factory set to two (2) hours. After thirty (30) days has elapsed, the IntelliChlor SCG will automatically set itself to a three (3) hour self-cleaning cycle. This feature will clean the IntelliChlor SCG blades more often during the initial installation, then go to a more standard self-cleaning cycle for longer cell life.
 

KurtinTUS

Silver Supporter
Jul 20, 2017
67
Tucson
So I'm updating this thread because I finally decided to give borates a try, and it seems to be making a big difference! Right on schedule this Spring, as the chlorine demand went up, so did reemergence of the white flakes. This is the third summer since the pool was built, and with a drain/refill already planned for this winter, I figured there wasn't much to lose by giving borates a try now. My current levels:

IMG-5450.PNG

The borates level is based on PoolMath (I don't have any test strips yet). I wanted to start on the low end of the recommended levels, so per PoolMath, 30 lbs of borates should get me to about 35. That seems to have virtually eliminated the white flakes in the pool, and greatly reduced scaling inside the SWG. It's made a believer out of me! :)
 

Saturn94

Well-known member
Mar 11, 2015
1,027
SE Virginia
Good to hear borates helped. 🙂

My understanding is that borates significantly reduces the pH jump that occurs inside the cell when producing chlorine. So it makes sense with borates added you would see less calcium precipitation occur in the cell.
 
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