Chlorinator Scaling

[Frbrostrom]

I have had an AquaCal AutoPilot Chlorinator for 3 years. I have always had near perfect water and watch the chemistry very closely. Until recently I have never had to use muratic acid on the chlorinator cell due to the fact that there was no calcium build-up. Recently, I received a warning that the cell needed maintenance and discovered heavy scaling. I cleaned the cell and was back up, but within a few days the calcium was back. My chemistry is still good but the Total Dissolved Solids are at 5,000. Salt level is very high but is recommended by Aquacal as not to stress the cell so much.

Do I need to drain the pool, or replace the cell?

 

[tim5055]

Welcome to TFP!

That you are reporting TDS numbers tells me you ar easing the pool store for testing. Most pool stores are very poor at testing on a good day. You need to pick up one of our recommended test kits and take control of your own testing.

I recommend the TF100 fro TFTestkits.net.

 

[Paul.]

When you say Salt level is really high, how high is it?

Is it measured by the pool store or by your own test kit?

Would you mind posting full test results?

 

[Frbrostrom]

Okay, I had it tested at two different locations and using two different methods. Despite the issue of accuracy, I am having the scale build-up quickly on my plates. Any idea as to the best way to stop the build up as soon as possible?

 

[Paul.]

I would use 1 gallon water to 1 quart muriatic acid to clean the cell, while we figure out the problem.
Your CSI may be way off if your Salt levels and other elements are not in balance.
Full test results will help with the troubleshooting

 

[Frbrostrom]

Some of the numbers below are in ranges because I have reading from 2 separate chemistry analysis techniques which were slightly different

Temperature between 78 and 80 degrees
Chlorine, free and total was 4
Combined Chlorine .19 ppm
Salt was 3900 to 4100 (usually keep this above 3700 to make it easy on the chlorinating cell)
PH is 7.6 to 7.8
Calcium Hardness 200 to 230
Total Alkalinity 110
Cyanuric Acid 62 to 70
PHosphates 0
copper 0.2 ppm
Iron 0.4 ppm
TDS 5000 to 5300

 

[Paul.]

I tend to agree with tim5055 these results look like pool store figures,
They seem ok but something has to be off.
Calcium Scaling is usually caused by an imbalance in the water chemistry.

Can you give us more information about the pool? Materials vinyl/plaster/pebble etc?
How often do you run the SWG? What is the percentage?
Do you see any calcium scaling elsewhere in the pool other than the SWG?

I also consider 3900-4100 ppm of Salt too high. On average it should be around 3200. Many salt machine stop working around 5000ppm.


According to pool school "A white buildup on the cell plates, or thin white flakes of calcium getting into the pool, indicate a water balance problem which needs to be corrected to avoid ongoing problems."
Pool School - Salt Water Chlorine Generators

The cell life of a SWG is usually 3 to 5 years depending on how well it is maintained.

 

[jblizzle]

Nothing in those numbers points to a reason for scaling and thus reinforces why we do not trust pool store testing ... so if you want to know the state of your water, you need one of the Recommended Test Kits.

The scaling is usually due to the CH and pH being high ... your CH is actually on the low side, but the pH is a little on the high side. I put your CSI right around 0 worst case, so I would not expect the scaling to be very bad.

 

[JoyfulNoise]

White scale on SWG plates is a indication of calcium scale. What causes it is pool water that is not correctly balanced. More importantly, you need to understand that the conditions inside the SWG cell are not at all comparable to the bulk pool water. The pH inside the cell is typically much higher than the pH of the bulk pool water because of hydrogen gas generation. So, even if your pool water numbers look balanced or about right based on pool store recommended ranges (which, by themselves, are not typically correct), they can be way off with respect to the SWG cell. Calcium scale forms when the pH, TA and CH are too high. High temperatures (like those found in a spa) exacerbate the scale problem.

The bigger problem is that it is hard for us to help you because no one on TFP believes pool stores numbers are accurate. They can sometimes get pH and chlorine correctly measured but they are often dead wrong when it comes to CH, TA and CYA. So while the pool stores tell you that your CH is only 250ppm, chances are they are way off.

The trick for reducing scale inside a cell is to ensure that you calcite saturation index (CSI) is slightly negative. But, you can't calculate the CSI without good test values. And those good test values only come when you measure your own pool water. You can plug the numbers you have in PoolMath (you need to know your pool volume) and see where your CSI is at. Then you can report back and let us know if the number is positive or negative.


Sent from my iPhone using Tapatalk

 

[JamesW]

Besides chemistry, I would suspect that the box might not be reversing polarity or the cell plates are getting rough and attracting more scale.

 

[Frbrostrom]

Fan assembly stopped working. I am having the new fan assembly installed and a voltage meter to test the reverse polarity. The display window on the DG220 is showing that the reverse polarity is initiated appropriately, at 4 hours at a time, but not sure if the voltage is responding to an actual negative charge during the reverse polarity stage.

By the way, I believe what everyone is saying about store chemistry analysis. Seems you could go to several different pool stores and the numbers are never the same. I need to look into the self test that everyone is referring to.