Scaling or other chemical reaction with pool plaster

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C

Cetanorak

Well-known member
Jun 13, 2022
101
Wimberley, TX
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Swimming pool that conveyed with the purchase of our new home was built in 2016. Standard gunite and plaster finish, looks to have been dyed blue. I have been using Pool Math to keep my chemicals in order over that past year but we have noticed an increased amount of the "white, streaky, pitty" areas on the plaster of the pool. Can anybody comment on my current Pool Math log as it might relate to this condition in our pool. Let me know if I need to provide any additional information.

PoolMath Logs

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Your CSI overall seems very positive overall (meaning, too positive). You have lots of months (based on what I quickly saw in your logs) in the +.5 to +.84 range (especially a longer run of very positive CSI in the last year to 6 or so months ago), which can lead to scale staining overall in your pool.

You want to try and keep your CSI between -.3 and -.3 on plaster surface pools. Since your pool plaster isn't new (please correct me if I'm wrong in that assumption), it's very likely just calcium carbonate from the overly positive CSI.

You can try Jack's Magenta "Passive treatment" (which takes weeks or a couple months, YMMV) and keeping your CSI more negative in the -.3 range during that time with your initial Magenta treatment AND regularly weekly "maintenance" dosing with the Magenta. It involves running a low pH around 7.2, a low TA around 80, and CH between 250-350. This will allow the scale to dissolve into solution which, along with Jack's Filter Fiber, you can capture in your filter. (SEE ATTACHED instructions).

If you want the calcium carbonate staining to go away faster, and you don't have patience for a slower removal, you'd have to do the Jack's #2 "Aggressive" treatment plan, which uses a Sulfamic Acid product, bringing your pH down to around 5, TA to around 0-50, and a super negative CSI for a week or so (water is NOT swimmable during this time!!), and you will also have to read chlorine with TC (FC+CC) for approximately 3-6 weeks after the treatment because the chlorine reacts with sulfamate and will seem like you have no to little chlorine (even though you do!). The "Aggressive" treatment is much quicker, but much more work and management, and cost.

Also, you rarely seem to be testing CH, which is something you might want to check a bit more often, considering your likely scaling issues.

Before doing anything, I would -strongly- recommend you buy Jack's stain "test" removal kit so you can VERIFY what the stains are. As I'm merely making an educated guess what the stains are BASED on your CSI and Pool Math logs (and they like white/cream'ish to me?). The stain test will prove it (likely the one that will do the BEST for you is Jack's #2 Copper and Stain removal).

All this assumes your plaster isn't newly refinished in the last 12-24 months.... HTH

(One caveat, the only thing that makes me weary about the staining being calcium carbonate is the "pitting" you mention, so be SURE to test the stains as mentioned above using Jack's test kit before acting on anyone's advice, including mine! :) )
 

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jesse-99 said:
Your CSI overall seems very positive overall (meaning, too positive). You have lots of months (based on what I quickly saw in your logs) in the +.5 to +.84 range (especially a longer run of very positive CSI in the last year to 6 or so months ago), which can lead to scale staining overall in your pool.

You want to try and keep your CSI between -.3 and -.3 on plaster surface pools. Since your pool plaster isn't new, it's very likely just calcium carbonate from the overly positive CSI.

You can try Jack's Magenta "Passive treatment" (which takes weeks or a couple months, YMMV) and keeping your CSI more negative in the -.3 range during that time with your initial Magenta treatment AND regularly weekly "maintenance" dosing with the Magenta. It involves running a low pH around 7.2, a low TA around 80, and CH between 250-350. This will allow the scale to dissolve into solution which, along with Jack's Filter Fiber, you can capture in your filter. (SEE ATTACHED instructions).

If you want the calcium carbonate staining to go away faster, and you don't have patience for a slower removal, you'd have to do the Jack's #2 "Aggressive" treatment plan, which uses a Sulfamic Acid product, bringing your pH down to around 5, TA to around 0-50, and a super negative CSI for a week or so (water is NOT swimmable during this time!!), and you will also have to read chlorine with TC (FC+CC) for approximately 3-6 weeks after the treatment because the chlorine reacts with sulfamate and will seem like you have no to little chlorine (even though you do!). The "Aggressive" treatment is much quicker, but much more work and management, and cost.

Also, you rarely seem to be testing CH, which is something you might want to check a bit more often, considering your likely scaling issues.

Before doing anything, I would -strongly- recommend you buy Jack's stain "test" removal kit so you can VERIFY what the stains are. As I'm merely making an educated guess what the stains are BASED on your CSI and Pool Math logs (and they like white/cream'ish to me?). The stain test will prove it (likely the one that will do the BEST for you is Jack's #2 Copper and Stain removal).

All this assumes your plaster isn't newly refinished in the last 12-24 months.... HTH
Click to expand...

Thank you, @jesse-99

I have to admit that CSI and CH and the interaction of all of the chemistry variables in regards to scaling are things that I don't have a great grasp on. As a new pool owner, new TFP member and new user of the Taylor TF-Pro kit, I've been likely to myopically focused on FC/CC/TC and pH, primarily. I am going to have to read up on Calcium scaling and take a look into Jacks Stain Test.

The plaster dates back to the pools construction in 2016.

Looking over the TFP basics section with regards to CSI, I see that:

If there is too much calcium in the water, calcium scale can form on the pool and in the plumbing, and the water can become clouded with calcium dust. If there is too little calcium in the water, and you have a surface containing calcium (plaster / marcite / pebble / grout), calcium from the pool surface can dissolve into the water, causing pitting and deterioration thereby shortening the life of your finish.
Click to expand...
and
To prevent scaling, you should keep your CSI below 0.6 at all times. Pools with surfaces containing calcium also need to have their CSI above -0.6 at all times to prevent pitting.
Click to expand...

The symptoms that I see on the plaster does look more like pitting and I don't really see scaling on the pool tiles or cloudy water. So I suppose that I'm unsure whether I'm seeing pitting or staining,
 
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Think of CSI (Calcium Saturation Index) as how much calcium your pool can effectively absorb before it falls out of solution. When you have a NEGATIVE CSI, your pool water can absorb more calcium, when you have a POSITIVE CSI your pool water can't absorb anymore and it begins to fall out of solution and precipitate onto your plaster surfaces.

Play with the Pool Math app (when you're on the main Pool Math app screen, click on the CSI box) and you will find that the adjustments made to things like pH, TA, and CH all have a very important impact on CSI, while things like Salt, CYA and Water Temp have a lesser impact on CSI (but still effect it). In other words, if your CSI is +.60, and you want to get it to 0, you can lower pH, CH, or TA individually, or together, to reach your target CSI. It's all relationship based...

Feel free to ask more Q's! Happy to answer them if I can.
 
Thank you again!

I guess that my main question is how to determine if this is scaling or pitting, given that all of my Pool Math numbers are in range? I will do the full battery of TF-Pro tests again tomorrow morning to get a more current baseline...but if my CSI lands within the recommended range again, I really woudn't know which way to adjust to correct what I'm seeing on the plaster.

@jesse-99 Even though the problem looks to me like pitting (whiter spots on the blue-dyed plaster with tiny holes) you noticed that my CSI levels have been historically positive, which is the opposite scenario of what one would expect for conditions conducive to etching/pitting, right?

Since we purchased the house/pool last year, I also wonder if the previous owners (who were not TFP-wise, used a standard neighborhood "pool guy") might have damaged the plaster and we are seeing the damage continuing to slowly manifest even though we have kept the water chemistry somewhat better balanced (I hope).

Thank you for your assistance.
 
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@Cetanorak -- I would say that your CSI numbers are not really in the ideal -.3 to +.3 when I looked at your logs. There are very long periods of time (months it seems) your CSI was +.5 to +.84. Overall, I would say there's not much consistency to your CSI, sometimes its super positive, sometimes its more neutral, and other times it's a bit negative.

Real negative or real positive CSI isn't a disaster or problematic if it's short term. Meaning, if you're +.6 or -.6 CSI for a week, you shouldn't worry too much. But if you're keeping those levels the entire season, there will start to be a cumulative effect on your plaster with either calcium carbonate staining or calcium leaching out of your plaster. It's also VERY possible that -before- you took the pool over, the previous owners ran a very negative CSI for way too long (who knows what issues they created with poor water chemistry), resulting in some pitting that you inherited, and now your overly positive CSI, has filled in those pitted areas with scale. Hope that makes sense?

I wouldn't suspect how you add chemicals to have that effect, *IF* you are seeing the same thing everywhere in your pool. IF you are seeing that ONLY in speciifc areas where you typically pour MA into your pool, they maybe the plaster is etched severely in those areas because that's where you're always adding the MA, but I'm guessing based on what you wrote earlier , you're seeing it evenly across the entire plaster? Let me know if that's not the case... I can't imagine chlorine additions having any effect at all on your issue.

HTH! Fire away with more Q's if you have them.
 
Cetanorak said:
Thank you again!

I guess that my main question is how to determine if this is scaling or pitting, given that all of my Pool Math numbers are in range? I will do the full battery of TF-Pro tests again tomorrow morning to get a more current baseline...but if my CSI lands within the recommended range again, I really woudn't know which way to adjust to correct what I'm seeing on the plaster.
Click to expand...
I forgot to comment on this... There's probably not much need (IMHO) to adjust anything major yet until you first perform the Jack's staining test and see what you find? Focus on that and let's see what you find? ... before focusing on adjustments.
 
one other thing I'm realizing is that the way that I'm using the PoolMath app may not be presenting an accurate picture of my CSI

I tend to test the pool at the end of the day once we finish swimming, I enter those results in to Pool Math and then add the necessary chemicals to rebalance (generally only Cl and MA). If the tests revealed FC of 3 and pH of 8.2, I will add the necessary liquid chlorine and Muriatic acid to achieve say FC of 6 and pH of 7.6 but I'm not retesting after circulation and entering those new levels into Pool Math. The next test and log would be after the next day. So the corrected CSI levels never really make an appearance into the Pool Math logs.

Is that a problem for obtaining an accurate depiction of pool chemistry over the long term?

Should I be logging differently in Pool Math?
 
Gotcha and that makes sense. "How" you log in the Pool Math app is really up to you. You can test/log before -and- after the chemical additions or only test/log before the chemical additions are made, then note the chemical additions themselves by using the Add Chemicals option, and not bother to retest until the next day or whenever you schedule your testing intervals. Not sure there's a right or wrong way to do it or log, so long as you have consistency and you have a feel for what your CSI is overall.

Speaking only for myself, I test regularly (I'm a testing addict, lol), so I know where my CSI is always at and can speak with high confidence where my testing values are, at all times, and would guess that you will get a feel for where you are with CSI (regardless of how you log) once you pay more attention to it overall? It really has to do with how often your testing and how long between those tests.

For example, you might test/log pH at 8.0 on Monday afternoon, and add some MA, knowing your pH will -likely- come down to 7.4 (based on your past experience), but then ma8ybe you don't test/log pH again until Thursday afternoon and your pH is back up to 8.0 again on that test (because of high TA, or because of aeration), so you log 8.0 again in Pool Math. But as you said in your post, it's not taking into account that maybe pH was 7.6 on Tuesday, and 7.8 on Wednesday, before you re-tested on Thursday at 8.0 again. So in that case, your CSI may read in Pool Math as being a lot higher (overall) than it truly is, because you're not logging the testing -after- the chemical addition.

So yeah, there's no real right or wrong way to do it. Some people log before and after, some log before and after and hte chemical additions, some only log before, some log before -and- the chemical additions afterwards, etc.
 

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@onBalance that section on "Scale V. Porosity" was quite illuminating. I feel as if what I'm witnessing is porosity and I do have to wonder about the plastering during the construction of the pool.

Having bought the house/pool from the original owners who built the house/pool in 2016, I attempted to contact the original pool builder over a period of a few months to get some basic info on the pool and to inquire about the "gunite warranty transfer" that he claims to offer the original owners...saying that he will honor the transfer of the warranty when they sell their home. He finally responded and was very uncongenial and unprofessional. He basically stated that if I wanted to transfer the warranty, it would require an inspection and that the inspection would cost $7,500. I have since discovered that he has changed his business name multiple times in the past 10 years and has horrible reviews linked to all of the old business names. He basically sells the pool design and then just subs out the work to random crews, who also sub out the work and that leads to the type of an experience and final product that you can imagine.

All of that to say...I wouldn't be surprised if the gunite or plaster wasn't mixed properly or applied effectively, resulting in this porosity.
 
This looks like it might be copper stains.

Try a stain ID kit.

Do you have copper in the water?

Can you pull the cartridges and show them before and after cleaning?

Are the cartridges blue when you clean them?

Can you have the water tested for copper?

Stain ID Kit | Jacks Magic

jacksmagic.com jacksmagic.com


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