Self Cleaning frequency

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L

lborne

0
Jun 29, 2009
468
Vero Beach, FL
Large Calcium Pieces

I have recently discovered calcium pieces. They are dime and nickel sized flat pieces on the floor of the pool at each return. Recently, I added citric acid to remove some stains and the pH dropped significantly. I noticed the calcium after that. I vacuumed them up, rinsed the filter cartridge, and now 1 week later have noticed the chunks again.

I have never noticed significant calcium buildup on the SWG cell nor have I seen any deposits on the small electric heater elemements (same type of elements used in a hot water heater).

According to my numbers, I should not have any buildup, but I do have high Calcium Hardness. Not sure why that is going up because I am not filling the pool with city water, it is being filled by rain the past couple months.

Numbers as of tonight:

CL = 12 (a bit high I know)
pH = 7.6
TA = 100 (also a little high)
CH = 570
CYA = 70
Slat = 3500
Borates = 50
Temp = 90 F

Any suggestions? I plan to drop TA to 80 and drop the pool level if expecting a large rain to help lower CH.
 
Re: Large Calcium Pieces

If you plug your numbers into the pool calculator you will notice that your CSI level is about .16. Not a big deal in a non SWG pool. But in a SWG pool at the SWG the water tends to scale easier. Some SWG compensate for this by reversing. When they reverse they shed any calcium buildup. In your case with a CSI greater than 0 your SWG will have a tendancy to produce calcium and could show up at the returns. Is your pool new? That may be the cause of the increase in CH as new pools tend to increase in CH for some time when new.
 
Topics merged.

I'm having a problem with the calcium flaking off the SWG after it switches polirity to clean the plates. The pieces end up in the pool below the returns. I thought it was my numbers being a bit off. This is what they were the past week:

CL = 12 (a bit high I know)
pH = 7.6
TA = 100 (also a little high)
CH = 570
CYA = 70
Slat = 3500
Borates = 50
Temp = 90 F

I've since brought TA down to 80 and pH is at 7.2, but I'm still having the problem - possibly due to high CH??

Anyway, what are my alternatives? I can decrease the time between when the SWG switches polarity which should result in smaller pieces of calcium, but will that decrease the life of the cell? Or I could add a filter basket of net after the SWG. Suggestions?
 
Re: Large Calcium Pieces

I have verified that it IS my SWG cleaning itself. The fact that there are no particles in the spa since the SWG feeds into the pool only was a good clue. I am injecting acid (not full strength) right into the plumbing, so pH right at the cell should be a bit lower than the pool. I've also lowered pH to 7.2 and TA to 80 to see if that helps. So far, it has not, but I'll give it a day or two more.
 
It's the high CH that's doing it. The cell is working exactly as it's designed to. Calcium builds up on the plates and when it switches polarity it rejects the scaling causing it to be propelled into the pool. Just vacuum it up and be happy it does that! :)
 
High CH by itself does not do it. Keep in mind that in many desert/arid regions, calcium hardness elevates in excess of 1000 ppm...yet there are many systems operating without scaled cell issues.

If your SI is good, and in my opinion, +- .3 is considered good, the self cleaning should keep the calcium in solution. Usually when the Salt system is not reversing polarity properly, it will allow scale formation within a week. How did you check it to verify that the self cleaning is working properly?

Normally, there can be a slight calcium build up but it's virtually invisible, with balanced water conditions. The reverse polarity (self cleaning feature) dissolves any calcium that may develope, but it should not blow visible scale back to the pool/spa. If it does, then there are two possibilities:
1) SI is high and in a scale forming condition - this usually shows visible scale formations on the blades in a time frame of two weeks or longer. The only time I ever see scale in less time, with a properly working system, is if calcium chloride is used repeatedly for shocking purposes, with the cell activated.
This is corrected by testing and adjusting your water chemistry to ensure balanced water conditions.

2) Reverse Polarity is not working on the power supply - this is exhibited by the scale forming within a week. This is corrected by replacing the power supply, which contains the reversing relay.

If you remove your cell, do you see visible scale? How much or how thick it is? From your description, it's probably just between the blades, and not bridging over the ends of the blades.
Acid wash the cell to ensure all scale is dissolved, then put it back into service and observe if there is still a scale build up...and if so, how quickly is it building up.
 
Poolsean,

1. My SI is good. This all started about 2 weeks ago when I added citric acid and then baking soda. Never had this large of a calcium problem before.

2. The cell is building up the deposits in about 1 week time. In the 2 weeks since adding the above, I've noticed the calcium bits coming out twice with about a week in between.

3. The cell builds up a lot of deposit, but it is not very thick (less than a dime) and not building up between plates. I acid washed it yesterday and today there is a hint of white on the edges of the blades.

4. The reversing seems to be working correctly per the indicatiors that say 1 and 2. Is there a way to tell if it is not working correctly? Would only 2 of the 4 plates always be built up? My thought is that the self cleaning is working properly, but that the build up is much accelerated from before. Would changing the frequency of the polarity switching help reduce the problem and/or indicate if it was switching properly?
 
Poolsean,
On Aug 28 your numbers where were indicating a high CSI. On Aug 30 you corrected this by adjusting chemicals to bring your CSI negative. Now on Aug 31 you are saying that your CSI is good when in fact it has been high as early as three days ago. Keep your test results within acceptable values and with a slight negative CSI and be patient. If after a couple of weeks of having your test values negative and you continue to have calcium scaling at the returns then maybe there is something wrong with your SWG. Your signature line does not state what kind of SWG you have, what kind is it?
 
My CSI is good now (at least within +/-.3) and it is slightly negative now. I agree I need to give it a week.

SWG is a CompuPool. It seems to be working fine. It is keeping Chlorine steady at 50% output for 8 hrs run time and polarity seems to be switching OK - but that is based on the indicator lights.
 
If you can get directly to the cell terminals, you can check the voltage with a meter. Allow the system to run long enough then check again for the voltage, but make sure you place the same meter probes to the same cell terminals as the first test. If it is reversing polarity properly, it should switch from positive to negative (or vice versa).
If the CompuPool allows you adjust the reversal rate, a quicker reversal will help prevent the scale build up. Although finding the cause is really the solution, as the increased reversal rate will tend to deplete the cell quicker. However, the scaling will deplete it quicker than the reversal rate increase....the lesser of two evils.
 

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The SWG has 4 plates and 3 terminals. The terminals are covered when the cord is plugged, but I can attach a small lead from each to tap into with the meter. Why 3 terminals? Is one ground? Guess I need to look more closely at the cell.
 
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