Calcium Scaling/Stains

[bwright42tx]

So I am guessing these "stains" on my fake rocks for my grotto are some sort of calcium scaling from the PH being too high over the winter (didn't check the pool chemistry as often as I should have). PH is now undercontrol, but what can I do about these stains? Anyone know of any products that work good?

 

[257WbyMag]

Can you post a set of test results for us to see?

 

[Guest]

What is your CH level? That could very well be as much (or more) of the problem as high pH.

Where are you located? You may be able to have an R/O company come in and make the water slightly aggressive, which might pull some of the calcium off of the "rocks' (you would have to raise the water level to allow it to pull it back into suspension), and you could lower the pH to attempt to help do the same.

It may just be too much at this point though and you will need to drain and have the feature cleaned and repainted.

 

[bwright42tx]

Test Results as of last night:

FC 5
CC 0
TC 5
PH 7.5
CYA 70
TA 80
CH 280

Added 44 oz of Myuratic Acid to drop the PH to 7.2 (trying to get the ta down to 40-50 ish because I had PH rise problems all last year probably due to the SPa Spillover that is always aerating the water when the pump is running and then use of the waterfall).

Just did a quick color test this morning:

PH 7.2 (running pump and waterfall to raise the PH so I can continue to lower the TA)
TC 4.0 (It was late morning and the sun had already hit the pool, so not concerned about the FC drop)

I'm located on the north side of Houston, Texas. I pretty sure it's calcium scaling, just wasn't sure what if anything could be used to clean it.

 

[frustratedpoolmom]

Well, I found this old post, maybe you could try this?

You could use a dilute mixture of muriatic acid to test a small spot. Rinse well. Wait 24 hours after the test and recheck the test spot for any adverse effects to the stone. Start with a 10 to 1 mixture of acid and increase the strength if needed. If either one gives satisfactory results, then use that to clean the rock. You want to be very careful and use the minimum amount possible and rinse very well. You could use a dilute mixture of water and baking soda to scrub the stones to neutralize any remaining acid. Rinse well.

 

[257WbyMag]

Before you make any more changes to your water chemistry regarding TA and pH, it would probably be best to look at the your potential for scaling or corrosion right now, based on your numbers.

Have you found the Pool Calculator in Pool School? There is a link to it in my sig line.

Now, I don't have your water temperature, but by plugging in your numbers in the Pool Calculator and giving your water temp an estimate of 70 degrees, I am getting a fairly negative CSI reading which indicates that corrosion to surfaces, not scale buildup, to be your most pressing potential problem. These numbers (and the temperature estimate) give me a CSI of -0.53. This is very close to being a problem for your plaster and surfaces that come in contact with the water.

I would also raise the FC. Based on your CYA of 70, 5 ppm FC is the bare minimum. It should be closer to 8 ppm to be ideal.

As far as the ring around your water line, if it is related to calcium, you can try a stiff brush and a VERY dilute muriatic acid / water mixture and see if that will help. Remember though, anytime you apply an acidic material on your rocks or grout, you risk taking some material that you don't want to remove off.

 

[bwright42tx]

My pool water is a nice 86 degrees. As for the pool calculator, I have been using it. My CSI was a +.5 when the PH was > 8.2 and it will be at -.29 when I am done if I take the TA down to 60, so I guess I will stop there. I did not notice before, but it looks like adding borates will lower the csi as well. I would like to get my CYA down to 50 as well, I am hoping splashout and evaporation will slowly lower it, that will help with the CSI as well.

I am shooting for:

FC 4
TA 60
PH 7.6
CYA 50
CH 280 I think it's fine where it's at, let me know if I need to change this.

I am working on getting replacement bulbs for the ozonator and beleive with its extra oxidation help FC 4 at 50 CYA should be adequate even though its the min on the chart.

I would alos liek to add Borates bu want to wait until all the other water balancing is done.

I hadn't thought of this before, but will the Ozone oxidize the Borates? thus making that a waste of time?

 

[Guest]

Your CH is fine (very good actually!), but an 8+ pH is too high and needs to be fixed (sounds like you are on that!).

Is this a salt pool? Might just be salt staining?

And I'll second 257's comment; watch your dilution ration on the acid. It will remove paint, and possibly material.

 

[JasonLion]

The ozone and borates won't interact, so borates are fine.

 

[bwright42tx]

Been swimming today, and had the waterfall running and the spas spillover and the PH is still holding at 7.2. WHich is actually a good thing as I know it will climb again. I will stop my efforts to lower the TA for now and watch the PH more closely and see how rapidly it rises. I am assuming the high PH initially was what lead to the what I am assuming is caclium scaling/deposits on the rocks, as it was definately over 8.2. Unfortunately after experimenting with various dilution amounts of muratic acid and water, and both a nylon brush and a wire brush, it looks like any concentration high enough to remove the scaling also removes the paint/stain. That being said, I think I'll let time run its course and see if the lower ph water doesn't eventually clearup the problem on its own as water continues to splash over the rocks. If not at the end of the season I can do a partial drain and some work on the rocks, and as much as I hate to say it maybe even an acid wash for the whole pool. It's got a few rough patches (probably from not monitoring the PH closely enough during the plaster curing process a couple years ago and not brushing enough) and as much as most people around here disagree with it I think an acid wash this fall might be good for the whole pool.

I might decide to try a pressure washer before then on the rocks and see how that goes, I've got some areas of the house siding that could use a good pressure washing anyways. I know I've gotten completely off topic here and rambling a bit but is pressure washing a problem for the plaster? That might be better than acid washing the pool and I could do that myself..just drain, pressure wash, refill. . .