Getting rid of Calcium Scale

MorganJ

Active member
Jul 12, 2023
42
South Carolina
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Hi all, I've read a few things on calcium scale, but as always wanted to have a conversation before taking action. When I bought my pool the chemistry was off, and we had a bunch of scale at the bottom of the pool (picture below). I have a pumice stone, but I've found that it barely makes a dent in most of these, and it would take me 10 years to actually scratch each one off. Aside from a full drain, is there anything that can be done?
 

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Hello MorganJ... can you provide us with a full set of test results from your own test kit?
FC
CC
pH
TA
CH
CYA
Salt if applicable

That's going to help us a lot :). Thanks!

Maddie :flower:
FC - 12 (I'm slamming)
pH - 7.4
TA - 100
CH - 350
CYA - 30


The scaling has been there for over a year when the calcium Ballance was way off
 
Finish your SLAM.

Once that is complete, then address the scale. I suggest you lower the pool pH to 6.8 and hold it there.........perhaps for a long time (weeks, not days) Judge your progress but you should see a long, slow reduction in the scale.

I can't see from the pic.......are they calcium nodules?
 
As Dave is suggesting you can run your CSI at the low end of the range around -0.6 and it should slowly melt the scale off.

It can take as long to melt the scale as it took for the scale to grow.

Do you have PoolMath and CSI tracking turned on?

 
Finish your SLAM.

Once that is complete, then address the scale. I suggest you lower the pool pH to 6.8 and hold it there.........perhaps for a long time (weeks, not days) Judge your progress but you should see a long, slow reduction in the scale.

I can't see from the pic.......are they calcium nodules?
Does this help at all? Hard to get a good pic.

Obvious question is how do I avoid other issues cropping up if PH is low for that long, any recommendations?
 

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My understanding is that low PH makes the pool water irritating to swimmers and potentially damages equipment

Keep pH above 6.8, in the 6.8 - 7.0 range, as recommended and you don't have those issues. Don't go lower then 6.8.
 
Getting rid of huge scale deposits is easy!

1. Have your pool guy empty the pool and watch him do an acid wash.
2. Refill the pool and then watch your barely better looking finish bubble and peel off.
3. Then fight with your pool guy for half a year about fixing the finish.
4. Finally, sue him, win and get him to buy you a brand new pebble finish.

That's how I did it, and now... no more scale!

Point being, whatever you do, don't let anyone talk you into acid washing your pool to remove the scale. It won't work well at best, and you'll destroy your finish at worst.

I inherited the scale with the purchase of the house and pool. It was very clearly due to poor water chemistry the entire life of the pool (by the same pool guy). Now that I monitor my CSI via TFP methods, no more scale, and this new finish is now about as old as the original one was when it had aquired all that scale, so that's pretty much proof positive that maintaining the correct CSI works.

I might have tried lowering pH had I known to (I hadn't found TFP at the point in time). I have my doubts that's going to work, because even an acid wash (which is about as low a pH as you can get) didn't remove even 50% of the scale. But maybe a less aggressive pH over a much longer period of time will do the trick, the guys seem to think so. So I say good luck, it can't really hurt to try, and I hope it works out.

What I should have done is learned to like the finish as it was, accepted its faults and just lived with it until it was time to replace the finish at the 10-15 year mark.

Please do keep us updated with your process, as I'm rooting for you for the pH adjustment to work.
 

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Getting rid of huge scale deposits is easy!

1. Have your pool guy empty the pool and watch him do an acid wash.
2. Refill the pool and then watch your barely better looking finish bubble and peel off.
3. Then fight with your pool guy for half a year about fixing the finish.
4. Finally, sue him, win and get him to buy you a brand new pebble finish.

That's how I did it, and now... no more scale!

Point being, whatever you do, don't let anyone talk you into acid washing your pool to remove the scale. It won't work well at best, and you'll destroy your finish at worst.

I inherited the scale with the purchase of the house and pool. It was very clearly due to poor water chemistry the entire life of the pool (by the same pool guy). Now that I monitor my CSI via TFP methods, no more scale, and this new finish is now about as old as the original one was when it had aquired all that scale, so that's pretty much proof positive that maintaining the correct CSI works.

I might have tried lowering pH had I known to (I hadn't found TFP at the point in time). I have my doubts that's going to work, because even an acid wash (which is about as low a pH as you can get) didn't remove even 50% of the scale. But maybe a less aggressive pH over a much longer period of time will do the trick, the guys seem to think so. So I say good luck, it can't really hurt to try, and I hope it works out.

What I should have done is learned to like the finish as it was, accepted its faults and just lived with it until it was time to replace the finish at the 10-15 year mark.

Please do keep us updated with your process, as I'm rooting for you for the pH adjustment to work.
Dirk - this is exactly why I posted here, as many articles suggest acid wash is the only route. To be honest, I don't really care about the little white dots but in a perfect world I'd remove them .

Just to clarify, did your close monitoring of CSI and adjustments actually remove the scale, or are you saying that following a total reset you've just been able to avoid the problem coming back?
 
Great. I think I may wait until after swim season is over and attempt the PH reduction

Focus on CSI reduction not pH. pH is just a tool to reduce CSI.

CSI will reduce as the water temperture drops in the fall and winter so you will need less pH reduction to keep CSI around -0.6.
 
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Dropping the TA to zero might work, but you have to take the system offline while you do it and there are big risks to doing this.

Take the system offline, drop the TA to 0 and brush thoroughly several times.

If that works, raise the TA with baking soda and bring the system back online after the pH is back in a good range.

Sulfamic acid might work, but it will lock up the FC into CC for months.

This is manageable, but it requires some work and the heater should be offline.

You can drain and refill to get rid of the sulfamic acid if it is safe to drain and the pool will not pop up out of the ground.

Pools can float if drained, so never drain unless you are sure that the pool will not float.

A zero TA treatment (aka a No-Drain acid wash) is aggressive and it might cause more damage than you want, so be very careful.

Acid attacks and dissolves the cement in the plaster and causes the aggregate to become more exposed.

Exposed aggregate will be very rough and some will fall out due to the lack of cement.

Note: Do your own research and understand the risks before deciding what to do.
 
Just to clarify, did your close monitoring of CSI and adjustments actually remove the scale, or are you saying that following a total reset you've just been able to avoid the problem coming back?
The latter. I do see some scale at the water line, but I believe this to be unavoidable. I think that is caused by evaporation, not chemistry. Under the water line I have not seen a hint of scale since Nov 12, 2017. I know that date because I joined TFP the same week I got my new finish. I think the pool was about six years old when the finish was destroyed, but before the acid wash it was covered in scale, like really bad (way, way worse than yours). So I have seen first hand what the same pool subjected to high CH fill water looks like after six years, both with and without TFP. Granted it's just one pool, but I have a relatively unique test case for CSI management.

So no, I didn't attempt to remove existing scale by lowering pH or managing CSI.
 
 
I have to defer to most of your thread's contributors, as they have more experience with pools than I. But I did do a lot of research after my finish was destroyed, to help me determine what had happened (and who was at fault). What I pieced together, and what I now share, isn't generally disputed here when I do. Which is:

Acid washing doesn't magically attack the stuff you're trying to get rid of, while leaving your pool finish alone. No, it dissolves a layer of your pool off, which happens to take the crud with it (and usually not all of it). What you are left with (even when the acid wash is done perfectly) is less pool. There is no way around that. Less finish, less years of the life of your finish, and a significantly rougher finish at that. As James points out, with a pebble finish you get all that goodness plus some of your pebbles will fall out, too! That's after a good acid wash! A bad acid wash will leave pock marks, can create bubbles in the finish that then pop off, and worse. My pool experienced all of the above.

FullSizeRender-1.jpg

I've got a folder full of these pics, from all over my pool. This one is from the side, the bottom was way worse. That's the entire skim layer burned off. What you don't see is how rough to the touch the parts were that weren't completely burned off.

James also warns of the dangers of emptying your pool. Yes, it can float out of the ground under certain conditions. But there's more to that, too. Especially with an older pool. The water is part of the structure of a pool. The water pressure is pushing outward on the plaster finish. If suddenly removed, along with direct exposure to sunlight, all kinds of fun things can take place. The bubbling I described, and/or pop offs (weak areas of your finish suddenly free of the force holding them in place just pop off), etc. Blah, blah, blah. Don't empty your pool unless you absolutely have to, and never acid wash it. Period.

Now what I have no experience with is this "no drain" acid treatment. They'll correct me if I'm wrong, but this lowering of CSI/pH is some form of that, if just a less aggressive one. So now I'm just theorizing. But other than avoiding the dangers of emptying your pool, how is this going to be much different than an acid wash? It's just a more controlled one. How is the more aggressive water going to go after and dissolve just the calcium scale without also going after your pool finish? Sorry, not seeing it. Maybe others here can explain that.

If you force me to guess, I'd say even if you could somehow use these techniques to rid your pool of the scaling, you're going to reduce the life of your finish by some amount. I don't think anyone here can say by how much. And you'll never know either. When you eventually have to refinish, you'll never know if you had to do so a month sooner than you would have, or a year, or five years.

Just be aware that there is going to be some sort of trade off if you don't leave well enough alone. That trade off could very well be worth it to you, a nicer looking pool, but a little less life, maybe a little rougher feel. But that is not a guarantee, and there's no formula that you can ponder beforehand, you'll just have to roll the dice.

A final note.

One of the many refinishers I talked with told me his MO to avoid the dangers of a typical acid wash was to use a hybrid approach. He very lightly acid washes the finish (with a much reduced acid "strength"), only enough to kinda loosen things up, he said, and then he goes at it with manual abrasion. Basically sanding off the scale. He doesn't really avoid losing some of the plaster, but his process affords much finer control, and the ability to work on discrete areas as much or as little as needed. He can fine tune the material removal: more aggressive in the worst spots, little or no abrasion in areas that are less affected or not affected at all. And the sanding has the benefit of leaving the finish nice and smooth. You can somewhat vary the treatment from area to area with an acid wash, if you're really good at it (most guys are not), but not at all with a no-drain acid treatment. That latter MO is going to apply the same treatment of aggressive water equally to every square inch of your finish, whether they need it or not.

Put another way, you have already figured out how best to solve your scaling... by sanding it off. But that's a trade off, too, isn't it? Is a little better looking pool worth the effort you now know it's going to take?

Or you can squint your eyes a little while staring at your pool, and convince yourself you're looking at organic art, maybe a bit like looking at the Milky Way on a cloudless night. No muss, no fuss, cocktail in hand, and bob's-yer-uncle.
 
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