Yikes.... how do I clean heavy calcium build up on SWG cell?

[aztodd]

Hey all - I have been running a Circupool core35 SWG for ~1.5 years now.

Full disclosure, I didn't do any maintenance/checking beyond looking at the lights for the first year.

This past May, I took it out and saw there was some calcium (??) buildup on the cell, but much less than you see in this picture now. I cleaned it the best I could using a stiff nylon brush and was able to eventually remove most of it. Some chunks were still loose inside the unit though and I couldn't see how to get them out.

Fast forward to today, I went out to check and things have gotten far worse

I know using an acid solution is not ideal due to the corrosive effects on the actual plates... but I seem to be well beyond the point of cleaning this with just a brush and water.

I humbly ask for your guidance on how to thoroughly clean the cell, and also how to prevent this from happening going forward.

My guess is that I just let my pool spend too much time in the positive CSI range (pH loves to sit at 8+ and I don't add acid often enough). I thought salt cells were supposed to reverse polarity for part of the time while running to help prevent this from happening, but I could be misunderstanding this.

Pool math logs are in my signature.

Thank you in advance!

 

[ajw22]

Start with the gentle methods and work your way up.

SWG How It Works - Further Reading

www.troublefreepool.com

You should only clean a SWG cell if it has visible scale on the plates.

First try and use strong blasts of water to remove the scale.

You can scrape the plates with a stick, like a Popsicle stick, to remove the scale.

If the scale is stubborn then use cleaning vinegar (6% acetic acid … available in Home Depot). It’s milder than Muriatic Acid and won’t damage the ruthenium surface. Highly concentrated mineral acids are not good for the transition metal catalysts.

Cleaning a SWG cell with Muriatic Acid 10:1 diluted solution will remove some of the rare earth coating from the plates and reduce the life of the cell with every cleaning.

 

[ajw22]

Lower your TA to around 60 to prevent scaling in the SWG cell

TA - Further Reading

www.troublefreepool.com

Why Should TA be Lowered with a SWG?​

Usually a TA on the high end is fine if the pH is stable. However TA does need to be adjusted down with an SWG. The problem is, INSIDE the cell, the CSI is very different than in bulk pool water.

With high TA and aeration from the bubbles the SWG creates, you'll get faster pH rise inside the cell and so there's more potential for scaling. With current reversal, the cell tends to stay clean but you'll get more snowflakes out of the returns. Calcium hardness is only one part of the equation.

If the SWG cell pH rises much above 10 (and it can easily do that) and if there is sufficient levels of carbonate ions available (CO3--), then you will get calcium carbonate precipitation. The higher the TA and pH, the more carbonate anions are available.

Borates are particularly helpful preventing scale in a SWG because the pKa for boric acid / borate anion buffering is approximately 9. That essentially means you get the maximum buffering capacity at a pH of 9 and that tends to hold down the pH rise inside the cell. Keeping the pH below 10 in the SWG cell reduces the risk of calcium and magnesium scaling (insoluble magnesium hydroxide precipitates at a pH of 10.2 or so).

 

[mknauss]

Allen has provided a great path forward.

If you are not going to use softened water for make up water to control the CH, you really should use Borates. It will reduce the pH rise that occurs inside the SWCG cell and thus reduce the scaling issue. Regardless you need to control the TA.

As far as the polarity reversal, it will manage minor scale buildup. I call scale flakes from the SWCG a canary in the pool water. If you see those, time to address TA, and likely pH.

 

[aztodd]

Just wanted to follow up here, I tried using a popsicle stick but a lot of the gunk was just getting stuck inside the casing around the cell plates, which as far as I can tell is not able to be removed. I found a really great solution though. I used a waterpik to blast out all the buildup and that worked great. Now to get the chemistry in line and hopefully I don't deal with these issues again.

 

[Rattus Suffocatus]

I'll have to ty the waterpik. I am having severe scaling issues now and need to do a water change, but I am tying to wait until the monsoon is over with first. I use a ty-wrap instead of a popsicle stick and it works okay with my harder to get at Universal 40 cell. The way that unit is going I might replace the whole thing next year. It's starting to tick me off.