Large Stain on brand new plaster from Calcium addition

[gtemkin]

A little more than one week after Eden colored re-plaster job, pool startup person employed by pool contractor came over in the morning and added what he said was 3 "scoops" of calcium chloride. He briefly brushed the bottom where the calcium was added and left. I was gone all that day but the next morning I found an undissolved mass of calcium chloride at the bottom of the pool. Brushed it away and plaster now has a dark stain surrounded by a white ring. Pump has been running 24/7 since startup, water had been balanced during the first week for TA (baking soda), and maintained for Cl (liquid) and pH (muriatic) and no chemistry changes were being made at the time the calcium was added.

The pool contractor has been notified and attempted to brush the area with a stainless steel brush with no effect. At this time he's trying to contact his plaster expert for advise.

Here's a photo of what I found and what it looked like after a quick brush. Does anyone have any recommendations for a fix?

Thanks,

Gregg

 

[poolsupplysales]

That stain will not come out the pool will have to be replastered. you can not add calcium chloride to a colored plaster without pre disolving

 

[y_not]

Hi gtemkin,
Welcome to TFP!

Can you provide a full set of test results?

 

[Qwaxalot]

That stain will not come out the pool will have to be replastered. you can not add calcium chloride to a colored plaster without pre disolving

What he said
Your plaster guy has an expensive problem.

 

[gtemkin]

Sample taken immediately after dispersing mass of calcium at bottom of pool. Results are from local pool store analysis.

TDS 300
CYA 0
TCl .1
FCl .1
pH 7.6
TA 113
Adj TA 113
Total Hardness 96

I've added Chlorine and a little Acid since this analysis.

As recommended by poolsupplysales I have been pre-dissolving all my powder chemistry because I suspected the plaster would stain if I let anything stand on it for more than a few moments.

 

[houstonTex]

Wouldn't an acid wash remedy? Not ideal, but probably a good compromise between a re-plaster and just living with it.

 

[y_not]

Surely they don't have to replaster the entire pool? Couldn't they just drain it and then replaster just that 1 spot, as opposed to re-plastering the entire thing?
IE. Chiseling it out, then re-plaster. Feathering it in to match the surrounding surface?

Or is there some sort of dying process that could be done to re-color that spot?

Gtemkin,
If you're going to be keeping that water you should add stabilizer to it, CYA. If you don't, you will continually loose chlorine from the sun's UV rays and you'll never be able to keep up with it. Resulting in an algae bloom!!
You should also purchase your own test kit so you can be sure your results are correct. As the pool stores are extremely inaccurate.
See below for test kit info.

 

[gtemkin]

Pool contractor has finally come back and said they will be attacking the problem by sanding underwater using 80 grit wet/dry paper.

After reading all I have online about sanding, I have my doubts this will work for such a large area from an appearance standpoint and I'm of course concerned that it will reduce the life expectancy of the finish.

Gregg

 

[onBalance]

Hand sanding is an acceptable way of attempting to remove the stain, and from the picture, it really isn't all that large of an area. It may work.

 

[y_not]

Hand sanding is an acceptable way of attempting to remove the stain, and from the picture, it really isn't all that large of an area. It may work.

How do they then re-dye it?
Or is the idea to remove the bleached out area, down to unaffected concrete/plaster below. Past the layer that has lost it's dye and into a solid dye layer?

If so, if it's plastered, how does that work?
IE It's pretty thin, isn't it?

 

[onBalance]

The white stain is most likely a calcium deposit due to calcium chloride laying on the bottom of the pool. Hand sanding can easily remove the deposit without harming the plaster surface. The plaster finish is usually about an half-inch thick and the colored dye is also consistent through the entire thickness. Even somewhat hard hand-sanding generally only removes a "paper-thin" amount of plaster and the color would remain the same as the rest of the plaster finish. I prefer using 100 grit sandpaper which will leave the plaster surface very smooth and intact.

If by chance something other than calcium chloride was added, and instead dry acid was added that bleached the color dye out and etched the surface, the fact is that hard hand sanding would still be the best option to correct and remedy the discoloration problem. I am usually opposed to the "acid bath or treatments" remedies because they are often over-done and the plaster surface just ends up etched and rougher, and that definitely reduces the life of the plaster surface.

Replastering should not be necessary in this situation, and plaster patching would absolutely not work. Trying to "feather in" the plaster and color to match the rest of the pool is an impossible task.

 

[gtemkin]

Pool contractor wants to proceed with sanding and is asking that I heat the pool so his worker can do the job under water. The outdoor temperature this time of year in Seattle is mid 30's to low 40's. Pool water is currently at 41. Heard from my general contractor that the PC want the water heated to 80 to do the work. I'm guessing that would take a few days and a few dollars. Is there any danger to the pool itself going from 41 to 80 in that short a time? Do pools ever crack from sudden heating?

 

[Melt In The Sun]

No, but you may have trouble heating it that much. Do you have a heat pump or gas heater? Do you have a solar cover? A HP won't be able to do that, and you'll need a cover for the gas to get it to 80. It also will be a very large gas bill...who's paying that? You shouldn't be.

 

[gtemkin]

Thanks for the reassurance.

I have a 6 year old Jandy Lite2 LG250 (I believe that's 250,000 btu/hr). The pool cover is an automatic Coverstar (what they call a solid cover). The pool is somewhere around 25,000 gallons.

We usually take the chill off the water in the springtime and that costs about $350 going from about the mid 50's to the mid 60's. I'm guessing calling for 80 in the middle of winter is going to be 3 to 4 times that, and yes, he will pay for that.

 

[gtemkin]

The PC finally came by to attempt a fix without heating the pool up. I don't think he wanted to pay for any additional cost of heating the pool. His assistant had rigged up a water powered disc sander on the end of a telescoping pole. But first he tried dropping acid down a pipe followed by brushing. No effect. Then they lowered the disc sander down and as you can probably predict, it was uncontrollable, put some marks in the bottom of the pool and then they wisely decided to drop that idea. Here's a pretty awful picture with tiny red arrows showing the additional marks that were created.

Basically he said he'd have to wait untill springtime to do it right, which he's saying is underwater sanding. He moaned about the fact that it might involve the entire pool surface. He asked for final payment on the pool, but that's not happening until I'm satisfied with the fix.

 

[gtemkin]

Last week my general contractor came out and with help from one of the PC's key guys, went scuba diving to hand sand the stain. It didn't seem to have any effect and it was hard to tell that he had done much of anything. They came to the conclusion that the pool had to be drained so they could use power tools. Today he texted me that they want to go ahead with the drain and power sand, sooner than later. I replied with some ground rules/concerns.

1. The pool cannot stay empty more than a week. I've read that without water, the hydrated plaster can micro-crack and those areas will possibly show white discoloration over time. This is a colored plaster pool where whitening would be quite evident.

2. I asked that the work be performed during a dry spell. I don't know the sensitivity of sanded plaster to water drip type stains but it did rain after the plaster was originally applied and although the pool was covered with plastic, there are numerous water stains running down the walls starting at the bottom of the tile line. I live in Seattle so this may put things off for a while - if it really does matters.

3. The pool is very old style with an almost fully radiused bottom. I asked that the discs and backup pads they use have appropriate flexibility so they don't gouge the plaster, as happened with their first "sanding from the deck" attempt.

4. I let my general know that the PC should not think just sanding the stained area will be good enough. It's likely that a full pool sand will be required for a reasonable match, otherwise, why bother.

Do these seem like OK concerns or are any of them really not an issue? Comments are appreciated.

PS I ordered Randy Dukes "Pool Surface Problems and Solutions" to gain a little more insight into the subject. Hopefully that will come before they start.

 

[onBalance]

I like your ground rules. However, rain will not have the same effect now that the plaster has cured. So that type of streaking should not occur if it does rain a little. But you are right, it would be best to not have it rain.
And since it did rain when the pool was newly plastered and the plastic tarp didn't completely protect the plaster job, I suggest that you request that they sand the streaks as part of the deal.

 

[HouTex]

"He asked for final payment on the pool, but that's not happening until I'm satisfied with the fix."

Very wise. Absolutely don't pay them until they fix the problem. That's the only thing keeping these guys interested.

 

[gtemkin]

The PC tech came by with a Jacks Magic Stain Test Kit. He used the stocking method of touching the test powders to the stain and it appeared that powder #2 was the only thing that had any effect, It put a dark mark in the plaster.

Today the PC sent over a plaster consultant who put on scuba gear and repeated the Jacks test by pouring the powder directly onto the bottom of the pool. Again #2 darkened the plaster, although much more significantly than with the stocking test. He performed the test in both an unstained area and the stained area with similar results.

He declared, "copper", which is what apparently Jacks #2 tests for.

I guess I don't know how letting a load of calcium chloride sit on the bottom for 24 hours, and stain a 1 week old pool, will give you a "copper" problem but my guess is that the #2 powder is not only specific to copper, but other types of stains too. He thought the powder was Oxalic Acid based but he said Jacks doesn't reveal what it really is.

I haven't heard back from the head PC, who wasn't on site for this test, but it's looking like they're going to try a Jacks Magic treatment of some kind. I'm guessing he wants to try anything to avoid the cost of draining and sanding the pool. My concern is that whatever is done result in something that's going to last without additional expense on my end.

Here's a picture showing the spots where the #2 powder was applied. The original stain doesn't show real well in the picture. Anyone have any thoughts?

 

[gtemkin]

Looked a little further at Jack's #2 and it's called "The Copper and Scale Stuff". I'm not a chemist, but I'm guessing it's some kind of strong acid that will put copper - if present - into solution, and as I think is my case, will eat away at Calcium whether it be the stain or other parts of the plaster. Jack's markets this as, "Replaces need to drain and acid wash pool finishes".

Assuming the there isn't any appreciable copper in my water, will I have to go on a long term Calcium sequestrant regimen after this treatment or will the calcium that's put in solution just add to the current CH? My CH is at 290 and the plaster is 4 months old.