White crystals forming on plaster

[JamesW]

Just did this and yep it bubbled/fizzed right away and then completely disappeared.

Most likely calcium carbonate.

Keep the CSI at -0.3 and brush a lot.

 

[voidpointer]

I apparently put too much acid in so pH is 7.5 right now (I was aiming for 7.8). CSI with 950CH is -0.25. Would be closer to 0 I think if I was on target for pH.

 

[voidpointer]

Most likely calcium carbonate.

Keep the CSI at -0.3 and brush a lot.

And for educational purposes... calcium carbonate is the same as calcium hardness? Is that what forms when the CH is too high?

If 950 is indeed an accurate measurement, should I drain the pool to lower the CH?

 

[mgtfp]

What do you mean by "operating temperature"?

I mean the temperature at which you heat up the spa to use it. You said you noticed the crystals because they were poking your legs, so I assumed you are using the spa, but not at 57°F.

That's why I wanted to know if you heat the spa to use it in winter and how long the spa would stay at the elevated temperature.

CSI will rise as the water temperature heats up. To a certain degree this will be compensated by pH naturally falling with rising temperature, but I don't think all they way. So, the CSI in the spa while using it will likely be much higher than the CSI in the pool.

Your CSI is already at 57°F often around 0.3, and when heating it up to use it, you'll give it a CSI burst. And reaction rates speed up at higher temperature, do the effects of out if whack CSI show results faster the warmer the water is.

A water kettle scales up faster than your toilet cistern because water gets heated up in it, raising CSI and speeding up chemical reaction rates.

Those crystals could also be nodules, as @ajw22 suggested, which is a plaster defect, independent from water chemistry. But your water chemistry isn't great, so I wouldn't rule CSI related scaling out yet.

When you scrape off the crystals, are there small holes/cracks under the crystals, or just normal plaster surface?

 

[mgtfp]

This is from a different thread started in Jan, but I had some difficulties with my CH test and so another member suggested a different approach to the test involving dilution with distilled water. I posted the results here, but my CH came out to 950ppm which is a wildly higher number than I'm used to, so I suspect it's wrong. But since it may play a part with the crystals here, I did want to share the information.

Just read what you did in this thread:

I added 10ml of distilled water.
Then I added 10ml of pool water up to the 20ml mark.
I added 10 drops of R-10
Then 3 drops of R-11L
Then I got up to 19 drops of R-12. I do feel the shift to blue was quicker this time.

If I am doing the math right... 19 drops times 25 time 2 is 950ppm of CH??

I'm not sure if that's right.

You added 10ml of pool water and 10ml of distilled water and tested a diluted 20ml sample. In this case you don't multiply the result by 2, so that would have been 475ppm in that test.

 

[voidpointer]

I mean the temperature at which you heat up the spa to use it. You said you noticed the crystals because they were poking your legs, so I assumed you are using the spa, but not at 57°F.

That's why I wanted to know if you heat the spa to use it in winter and how long the spa would stay at the elevated temperature.

CSI will rise as the water temperature heats up. To a certain degree this will be compensated by pH naturally falling with rising temperature, but I don't think all they way. So, the CSI in the spa while using it will likely be much higher than the CSI in the pool.

Your CSI is already at 57°F often around 0.3, and when heating it up to use it, you'll give it a CSI burst. And reaction rates speed up at higher temperature, do the effects of out if whack CSI show results faster the warmer the water is.

A water kettle scales up faster than your toilet cistern because water gets heated up in it, raising CSI and speeding up chemical reaction rates.

Those crystals could also be nodules, as @ajw22 suggested, which is a plaster defect, independent from water chemistry. But your water chemistry isn't great, so I wouldn't rule CSI related scaling out yet.

When you scrape off the crystals, are there small holes/cracks under the crystals, or just normal plaster surface?

I probably heated up the spa intentionally 2-3 times since november. I didn't keep track. I usually heat it to 100F. There were 1 or 2 times the spa ran at night because I didn't realize the heater in standby mode will still kick on during freeze protection. When running it intentionally, the heater runs maybe 1 hour. Water stays warm much longer than that, though, because it stays warm in the spa.

Regarding holes or cracks in the plaster, I'll take another look but it's very hard to see any detail through the water given how small they are.

I've been a fan of the TFP method but CSI really frustrates me. The slightest fluctuation in pH results in either 0.3 or -0.3, especially in the winter. I thought it would be harmless to use my spa in the winter (after all, that's one of the main benefits of a spa to me) but this experience is making me think I shouldn't.

 

[mgtfp]

CSI is more a long term effect, I wouldn't worry about short term fluctuations. For you it's mostly the SWG you want to keep a slightly negative CSI for while it's operating.

I wouldn't worry too much about CSI getting a bit more negative over winter. Reaction rates slow down at lower temperatures, and the same negative CSI wouldn't have the same effect on plaster than it would have in summer.

 

[voidpointer]

I mean the temperature at which you heat up the spa to use it. You said you noticed the crystals because they were poking your legs, so I assumed you are using the spa, but not at 57°F.

That's why I wanted to know if you heat the spa to use it in winter and how long the spa would stay at the elevated temperature.

CSI will rise as the water temperature heats up. To a certain degree this will be compensated by pH naturally falling with rising temperature, but I don't think all they way. So, the CSI in the spa while using it will likely be much higher than the CSI in the pool.

Your CSI is already at 57°F often around 0.3, and when heating it up to use it, you'll give it a CSI burst. And reaction rates speed up at higher temperature, do the effects of out if whack CSI show results faster the warmer the water is.

A water kettle scales up faster than your toilet cistern because water gets heated up in it, raising CSI and speeding up chemical reaction rates.

Those crystals could also be nodules, as @ajw22 suggested, which is a plaster defect, independent from water chemistry. But your water chemistry isn't great, so I wouldn't rule CSI related scaling out yet.

When you scrape off the crystals, are there small holes/cracks under the crystals, or just normal plaster surface?

Thank you for this explanation it really helped. I heat the spa usually to 100F. Water temps have been in the mid to low 50s. So it's definitely heating up quite a lot. The thing is, though, I haven't used the spa that much this winter. Maybe 3-4 times since november. I didn't keep track of it. There were a few instances where I accidentally left the heater in standby during freeze protection. There is at least 1 time where the heater was running all night during freeze protection (well, for the period of time it was in spa mode at least).

Again the 0.3 CSI in my logs is somewhat misleading. I haven't been sure how to best log data. I was taught on the forums early on not to worry about adding acid until my pH hits 8.0. Since my test only has 7.8 and 8.2, I round up to 8.2 then I add. So yes, for a window of time my CSI is 0.3-ish, but when I add acid it should go down to just below 0. Maybe I'm doing this completely wrong but my actions are a reflection of what I _think_ I'm learning from others here on the forum. Not placing the blame on anyone here, but it is an expression of frustration to how complicated maintaining everything has been since there always seems to be competing concerns and my pH isn't stable at all. Even in the winter I'm still going from 7.5/7.8 pH to 8.2 over 3 days on average.

So basically, I test first *then* I add acid, so while my test reads 8.2pH, it's actually 7.8 or so right after. One other way I've tried doing it is adding acid first, setting a timer for 30 minutes, and then coming back to test. This means I accurately show a pH of 7.5/7.8, but it means I'm adding pH without first verifying I actually need it (the test isn't done first). It's a frustrating catch 22.

When I scrape off the crystals, I don't see any cracks or anything. The plaster surface appears to be smooth and looks the same as usual. It looks to me like the calcium just latched to the plaster and built up into little chunks. Not sure if that's chemically how it really works though.

My concern is two fold:

1. How should I recover. Someone suggested lowering CSI (dumping more acid in the pool) and brushing. But in other threads I've been told I am keeping my CSI too high, resulting in a higher CH due to possibly my plaster being eaten away by the acid. I was told to keep it just below 0 which is why I adjusted my MA addition to 12 ounces (it was higher before).

2. How to prevent this in the future. I like to use the spa in the winter, as I may have said already. Does this mean I shouldn't use my spa in the winter? Or is there some kind of balance to strive for?

I want to learn from this experience. I appreciate all the educational information so far. I am still confused about what calcium carbonate is and phosphates are and stuff; it all feels too scientific to me, but I'm happy to read more about it if someone can send me easy reading material.

 

[onBalance]

Are the "crystals" random and spread out a few inches apart? If so, then IMO, the problem may be a plaster defect and not a water chemistry issue. Although the crystals appear to be calcium carbonate, that does not mean that the water is out of balance and precipitating out calcium carbonate crystals on the plaster surface.

The quality (or lack thereof) of the plaster material in the spa could be very different from the plaster material in the main pool. If so, then the plaster material in the spa should be analyzed to determine if there is something amiss. That may be the only way to determine the problem for the crystals developing. Obtaining a sample of plaster from underneath the drain cover may be possible and then sent to a cement lab for analysis.

If you don't want to have your plaster analyzed, then I suggest simply sanding (with 80 grit sandpaper) the crystals to remove them and make the plaster surface smooth again. The crystals may not return.

Reading the following article may answer some of your questions.

Unusual Calcium Nodules

Calcium Nodules In 1998, the onBalance team published a paper in the Journal of the Swimming Pool and Spa Industry (JSPSI) on calcium nodule formation. The paper provided the science and mechanics for the cause of calcium carbonate nodules developing in pools. It explained that delaminated...

www.troublefreepool.com

 

[voidpointer]

Is it worth it to have the plaster analyzed? I'm not sure how painful or costly that is. I also am not sure how to find a cement lab near me. Any tips there would help.

I did read the article and the formations pictured there do seem very close to how mine looks. For example I do see a few calcium formations that look like "strings" but those must be just forming along the plaster as a line instead of just a "hair" sticking out. Based on the pictures there, it doesn't appear that I'd notice any cracks looking through water.

There was a lot of decent explanation as to how chemistry might be the cause, especially convincing considering I am only seeing these in the spa so far. I guess the point of the cement lab analysis is to rule out one of those.

 

[ajw22]

The point of the cement lab analysis is to have facts during your discussion with your builder about the warranty work required to replaster your spa.

If you have defective plaster that is cracking the only remedy is a complete chipout and replaster.

 

[onBalance]

Bad water chemistry does not cause random and isolated nodules. Did you notice the photo of calcium scale and the uniformity of that water caused problem? That is the significant difference.
At this point, we don't know if this is a serious plaster problem or not. Sanding the nodules may resolve the problem to your satisfaction.
The first and initial plaster analysis would cost about $150. The sample could be mailed to a lab.
Chipping out some plaster material should take about 15 minutes.
It probably would be best to wait until the weather and pool water warms up to closely inspect the plaster in the pool.
When convenient, I suggest you drain the spa and inspect the nodules up close, including tapping the surface with the plastic end of a screwdriver and listen for a hollow sound, and looking for small cracks. That needs to done to determine the condition of the plaster bonding to the substrate.
Lastly, nodule formation may indicate a significant and serious underlying problem.

 

[voidpointer]

The sample could be mailed to a lab

Would you (or anyone) please recommend a lab I can send a sample into? I assume once I have that, I can figure out what kind of sample they need and how I should obtain it. I know to get it from under the drain cover but I don't know what tools to use, or what size of a sample to obtain.

 

[voidpointer]

I drained the spa and took a closer look. I noticed significant plaster damage under one of the waterline tiles. Other than that, I was able to get much clearer pictures of the nodules. I don't think my eyes or phone camera magnify enough to see any cracks, but I do see what appear to be vertical lines that the calcium is "growing" along. There's a lot of pictures so I'll just link to my Google Photos album instead of attaching them all here.

Definitely looks like some repair work is needed either way. At this point I just need to figure out if I need to wait on the concrete lab analysis before contacting my PB. Sounds like I should do that based on the advice I've received here so far.

13 new items by Robert Dailey

photos.app.goo.gl

EDIT: One other item of concern is that since my first pool builder walked from the job before plaster, the PB I'd reach out to might try to shift liability to the first pool builder's shoddy gunite work. I'm not sure what kind of resistance I'll get, but I just want to be prepared to make the argument for receiving warranty repairs in this case. I'm not sure if the gunite itself could cause this kind of damage & nodules.

 

[ajw22]

This cracking is concerning and your spa definetly needs repairs.

You have enough cracking and visible calcium nodules to start a conversation with the builder and plaster contractor about the problems and see what they say.

You can take the plaster sample and do the lab testing later if you get resistance from them and need more evidence of defective plaster application.

 

[mgtfp]

Good photos. Does look like plaster damage I'd say. Also interesting that the plaster seems wetter around the calcium deposits, as if the plaster is more porous there, and moisture seeping through from underneath.

 

[ajw22]

As I said before you can use a paint scraper and scrape off the calcium from each nodule. There is a good chance they will stop growing.

The cracked area is what needs repairs.

 

[voidpointer]

Thank you everyone. I've reached out to the PB, we will see what they say. In the meantime do I leave the spa drained? I'm guessing not. Because the pool has too much water in it right now.

 

[ajw22]

I would fill the spa to normal.

You can easily drain it down anytime you need to.

 

[mgtfp]

And make sure that pH is where the PB will want to see it, don't give him a chance to distract from the root cause.