White scaling on my new waterfall & disagreement amount chemical levels

[Twolabs]

We just finished up our pool in November complete with a slide/grotto/waterfall feature that was constructed entirely out of gunite.

When we had our first big cold snap a few weeks ago (it may be just a coincidence), I discovered when the waterfall was off, there was a white residue forming on the areas where water flowed. Some areas were more noticeable than others, but it has made a fairly noticeable effect of dulling down the colors of the waterfall, and in some areas you can see streaks of this white substance. (Pictures below).







I contacted the PB, and he contacted the sub who did the work. The sub said they were going to come up and take a look at it, and then the PB called and said he wanted to take a water sample (which I knew was coming). However, I felt pretty comfortable because I've been fairly on top of my levels ever since it was completed. Right now my levels are hovering around, and have been for the past few weeks:

pH: 7.5 to 7.6
FC: 3-5
CC: 0
TA: 70-80
CH: 225-250
CYA: 40

However, he just called and said, "The water tests came back and your alkalinity is 160." I kindly said I don't think so and asked where it was tested, and he said some pool superstore there in town, and that "The computers are fairly accurate. And your PH was high too. With Alkalinity that high, that can cause scaling." When I told him that I'm using a Taylor TF100 kit, considered to be the most trusted in the industry, he said, "Well sometimes those kits can be a little off."

He said I should try to test it again when I get home.

Now, I'm kind of concerned. I posted a couple of weeks ago that I left my test kit outside overnight and if that would have any effect, and the general consensus was most likely not.

So I'm going to test it again tonight when I get home. I might also take a water sample to a small time pool store close by to see what they say. Right now I feel like its my word against this "pool superstore"s word, and I'm sure my PB is thinking that I don't know what I'm talking about and my levels are all off.

Any ideas?

 

[Ryno98]

My thoughts: So what if your TA is 160. I plugged your numbers into PoolMath - your CSI is still -0.19 vs -0.59 with TA 70 (assuming 50 degree water - but still only 0.09 with 80 degree water!). Yes, higher TA leads to higher CSI which can lead to scaling, BUT - your TA would have to be off the charts to make any significant difference (around 1000 to get a CSI of +0.6). My gunite rocks have similar marks, but generally mine are more confined to a few corners or grooves and not as wide-spread. I still don't know what the marks are, and I'm still not convinced this is typical scale rather than concrete efflorescence or some other deposit. I have not tried acid washing, but they certainly don't brush off.

I think the PB is trying to approach this the wrong way. This is not about a "is it or isn't it" situation with the TA. It's about figuring out what the heck the deposits are and then how to remove them, independent of anyone's potential mistakes. He needs to be re-educated with regard to the effect of TA on scale/CSI.

FWIW, my TA usually runs around 50, and my CH is only 175-200. And I still have the white marks.

 

[Divin Dave]

I suggest you test your water with the TF100 several times and record the numbers.
Then get several samples of water and take a sample to several pool stores and get copies of each pool store result.
Try not to let the water sit in a jar for too long as this will effect the results.

Thats what I would do.

If there is another TFPer in your area, hollar at them and maybe see if you can get them to come over with their TF100 test kit for testing kit comparison to yours.

 

[JayBauman]

Any idea how much time elapsed between water collection and water analysis? What container was used?

 

[JamesW]

What was put over the gunite to make it look like rock? Was a sealer applied to the waterfall?

 

[Twolabs]

Try not to let the water sit in a jar for too long as this will effect the results.

If there is another TFPer in your area, hollar at them and maybe see if you can get them to come over with their TF100 test kit for testing kit comparison to yours.

This may be an issue. The pool guy (not the owner, but his supervisor) was the one that came and took the water sample. He had it tested back in the pool store in his town. So even if he drove straight from my house to the pool store without stopping, it would be 1 hr and 15 minutes at the very least.

As far as I know, no TFPers close to me. Except for you and Ryno, which are both located in the hometown of my PB. So, have any plans this afternoon

Any idea how much time elapsed between water collection and water analysis? What container was used?

No idea about the container, but see above about how long. No sooner than 1 hr 15 minutes, maybe longer if he made other stops or didn't go straight to the store.

What was put over the gunite to make it look like rock? Was a sealer applied to the waterfall?

There were at least three more materials of some sort put over the initial gunite. The first looked just like regular concrete (see below)


It was mixed with a traditional rotating mixer and carried over in 5 gallon buckets (and it looked extremely heavy), and applied with trowels. They used this time to roughly form the boulders. After that was put on, they went back over the areas that were going to touch water with some type of material (I didn't get a good look) that went on with a paint brush. I think it was some type of waterproofer. Finally they came back over with a mud-type of material and stamped it to make the impressions of natural rock. Then a light coat of spray paint from an air gun.

No final sealer was put on. They did ask me, and without any reason to do it I declined as I was afraid it would made the rocks have the "wet" look all the time and not more natural looking.

To the PB's credit, he has been on top of getting a hold of the sub. When the supervisor first called me back with the pool store test results, he asked if I'd try to scrape it off or use some type of diluted acid to get it off. I said I hadn't because I didn't want to mess with any of it until they had looked at it. He suggested that I try. Then about 15 minutes later, he called back and said that the PB (owner) had spoken with the subcontractor who told him, "Don't do anything to it. Leave it as-is. We'll take care of it, but we want to see it how it is now." So, right now they are still supposed to come take a look (a 5 hr drive one way).

I tested the water again last night and the pH is rock solid stable at 7.5-7.6 (I haven't had to had acid in weeks, which surprises me) and the TA was exactly 80.

With so much aeration from my waterfall freeze guard, I would've thought the TA would've risen.

I'm starting to question my TF100. I'm thinking I'm going to go ahead and reorder the TA reagents and Phenol Red just to be on the safe side and compare with my current kit.

 

[JamesW]

It might be scale, but I don't think so. I suspect that it is something related to the finishing materials. You can try putting a tiny drop of muriatic acid on a spot to see if it bubbles or removes the white. That would be indicative of calcium carbonate scaling.

Note: Even with balanced water, waterfalls will build up scale due to water evaporating and leaving behind any dissolved solids.

 

[duraleigh]

Your test results are likely just fine. More importantly, even if the TA is 160 (I doubt it), you do not have an obvious scaling condition.

Like JamesW, it looks like the coatings/sealants, etc. are causing that and not calcium scale......at least not calcium scale from you water being out of balance.

Again, as JamesW says, you will experience some degree of buildup on a waterfall regardless.

Before you doubt your testing (and the TF-100) keep in mind the thousands of us who use the same kit and have been for years and it repeatedly returns the most dependable results of virtually any testing available.

Obviously I have a dog in the fight but your issue is not a testing issue...........I am virtually positive.

 

[Twolabs]

Your test results are likely just fine. More importantly, even if the TA is 160 (I doubt it), you do not have an obvious scaling condition.

Like JamesW, it looks like the coatings/sealants, etc. are causing that and not calcium scale......at least not calcium scale from you water being out of balance.

Again, as JamesW says, you will experience some degree of buildup on a waterfall regardless.

Before you doubt your testing (and the TF-100) keep in mind the thousands of us who use the same kit and have been for years and it repeatedly returns the most dependable results of virtually any testing available.

Obviously I have a dog in the fight but your issue is not a testing issue...........I am virtually positive.

Completely understand and agree. And I was certainly prepared for some type of buildup to occur (i.e. We have small calcium buildups on the shower heads, etc) but didn't expect it to be so noticeable and so soon (in the matter of a month).

The only reason I was doubting my TF-100 was because I accidentally left it outside in freezing weather for a couple nights while out of town for Christmas. I went ahead and ordered some refills anyway just be sure.

One other thing my wife and I were discussing this morning that slightly debunks the scaling issue is, there are zero deposits of this type of substance on the flagstone spa spillover, waterline tile, or flagstone beach entry. If it were truly some type of scaling, wouldn't it be forming on those other types of material?

 

[pragmatic]

It’s definitely a type of calcium scale. Here’s the way I understand it; it's a process of “leeching”. Occurs when higher levels of calcium in the concrete migrate to lower levels (your pool water) and form a type of carbonate at the surface (interaction with air). In essence the pool water is pulling minerals from the concrete. Concrete/Cement/Gunite all contain levels of calcium / limestone (used as a binder/clinker). Calcium chloride can also be added to cement in higher concentration to increase cure time (ideal for forming structures-like a pool waterfall). I’m afraid It will be a battle and may dissipate over time, but the question is? 1) Do you try and seal? Not likely gonna help and it’s a pain 2) Increase CH of your pool water to reduce migration / leeching (concentration comparison). 3) Clean with HCl (Muriatic acid) often-the longer you allow the build-up the more difficult it’ll be to remove. Maybe all three? These are my thoughts and may not be totally accurate, but the basics of what is occurring is simple. Someone please correct if I’m wrong. Maybe ChemGeek will set us straight

 

[JamesW]

Some sealers will turn white when exposed to water. I think that that is the likely cause. If you dip a q-tip or tooth brush in some muriatic acid, and then use that to scrub a tiny test spot, that should help diagnose the cause.

 

[duraleigh]

Pragmatic,

You are pretty much describing efflorescence, wherein minerals migrate from the pool walls and turn to solids once they reach the surface.

Calcium scale generally refers to the soluble calcium in the pool water which, under favorable conditions, precipitates from the water onto pool surfaces.

Efflorescence is not at play in this instance and it doesn't really look like normal calcium scale, either. It's always tough to "guess" with pictures and test results but I think JamesW has identified it.

 

[pragmatic]

Gotcha! Thanks

 

[Divin Dave]

As far as I know, no TFPers close to me. Except for you and Ryno, which are both located in the hometown of my PB. So, have any plans this afternoon

Man, I apologize for getting back to this party so late. I certainly would grab my trusty test kit and lend a hand. I will be happy to help tomorrow afternoon (Thursday) if you still need it.

This may be an issue. The pool guy (not the owner, but his supervisor) was the one that came and took the water sample. He had it tested back in the pool store in his town. So even if he drove straight from my house to the pool store without stopping, it would be 1 hr and 15 minutes at the very least.

As far as I know, no TFPers close to me. Except for you and Ryno, which are both located in the hometown of my PB. So, have any plans this afternoon



No idea about the container, but see above about how long. No sooner than 1 hr 15 minutes, maybe longer if he made other stops or didn't go straight to the store.



There were at least three more materials of some sort put over the initial gunite. The first looked just like regular concrete (see below)


It was mixed with a traditional rotating mixer and carried over in 5 gallon buckets (and it looked extremely heavy), and applied with trowels. They used this time to roughly form the boulders. After that was put on, they went back over the areas that were going to touch water with some type of material (I didn't get a good look) that went on with a paint brush. I think it was some type of waterproofer. Finally they came back over with a mud-type of material and stamped it to make the impressions of natural rock. Then a light coat of spray paint from an air gun.

No final sealer was put on. They did ask me, and without any reason to do it I declined as I was afraid it would made the rocks have the "wet" look all the time and not more natural looking.

To the PB's credit, he has been on top of getting a hold of the sub. When the supervisor first called me back with the pool store test results, he asked if I'd try to scrape it off or use some type of diluted acid to get it off. I said I hadn't because I didn't want to mess with any of it until they had looked at it. He suggested that I try. Then about 15 minutes later, he called back and said that the PB (owner) had spoken with the subcontractor who told him, "Don't do anything to it. Leave it as-is. We'll take care of it, but we want to see it how it is now." So, right now they are still supposed to come take a look (a 5 hr drive one way).

I tested the water again last night and the pH is rock solid stable at 7.5-7.6 (I haven't had to had acid in weeks, which surprises me) and the TA was exactly 80.

With so much aeration from my waterfall freeze guard, I would've thought the TA would've risen.

I'm starting to question my TF100. I'm thinking I'm going to go ahead and reorder the TA reagents and Phenol Red just to be on the safe side and compare with my current kit.

 

[chem geek]

Waterfalls are tough to keep calcium carbonate free in a plaster pool because the water is aerating and getting higher in pH and there is some splashing and evaporation. So getting some calcium carbonate is inevitable. If the white deposits are more in the areas near but not in water, then it's probably splashing and evaporation. I can see some of that in your photos. I'm guessing that because the rock is fairly new, the continuing curing made the surface particularly high in pH so splashing and evaporation would be more likely to form scale that sticks as opposed to dust that would blow away.

About the only thing I can think of that might work is to use a calcium scale inhibitor product in the pool water. Such products aren't metal sequestrants, or at least that's not their primary mode-of-action. Instead, they inhibit the crystal growth of calcium carbonate by binding to small forming crystals causing defects or preventing them from adhering (i.e. they form soft scale that is filtered out as opposed to hard scale on hard surfaces).

 

[Swampwoman]

^just to possibly confuse the issue further...I get the same watermarks on MY fountain when I use pool water to fill it.

It is a fiberglass faux rock fountain independent of the pool. I have very low calcium in my pool water (vinyl liner with soft-ish water).

My marks will wash off with water, so I assume at least in my case its salt from the combo of using liquid chlorine and topping the pool up with softened water.

I know it's winter, but I have a hunch, based on my own observation on my fountain, that it may wash off

 

[easttn]

Right now I feel like its my word against this "pool superstore"s word, and I'm sure my PB is thinking that I don't know what I'm talking about and my levels are all off. Any ideas?

I read this on here the other day and I thought it was a good ideal in a situation like this. Get 3 samples from the pool in clean containers with no headspace and let 3 different people get test results from the same pool store and see how much they vary. One could be you, another could be the sub and the other could be the PB. When you get the test results ask them which test result are you supposed to use.

 

[zethacat]

This may be an issue. The pool guy (not the owner, but his supervisor) was the one that came and took the water sample. He had it tested back in the pool store in his town. So even if he drove straight from my house to the pool store without stopping, it would be 1 hr and 15 minutes at the very least.

Try taking a sample and letting it sit on the counter for 1 hour and 15 minutes then test it and see what you get.

With so much aeration from my waterfall freeze guard, I would've thought the TA would've risen.

Aeration does not raise your TA.

 

[Twolabs]

Good tips, I'll try that zetha.

And also good catch on that. Aeration raises pH (for some reason it hasn't raised ours?) not TA.

 

[Patrick_B]

Good tips, I'll try that zetha.

And also good catch on that. Aeration raises pH (for some reason it hasn't raised ours?) not TA.

The pH rise through aeration comes from the outgassing/liberation of Co2, and it's in the water largely as a result of acid reactions. If you haven't been adding a lot of acid that would help explain why. You have nice water up there so thank your lucky stars you don't have to fight pH like a lot of us with hard alkaline water.

As suggested by eastn above, do get some test reults from multiple sources if possible. There is a similar situation in another thread, and like many, your PB people probaly think these store tests are gospel. If so, this is a very prudent thing to do. Once you are comfortable with the tests like you are, trust your results. Period.

Lastly, It's a great idea to check out your tests if you suspet bad reagent, but I'm betting you don't have a problem with them. Double check with the new ones, and save the old ones until you are sure.