Calcium Test all of a sudden starts purple - Light Scaling?

[rhawke]

Hi!

So our new WetEdge Primera Stone Spa had some initial issues and they came to repolish it with these diamond blades. It got repolished and I started testing water chemistry daily and added PH since it rose a bit quicker than usual. Below the results that haven't changed much:

PH 7.6
Calcium: 275
TA: 70
Salt: 3000
CH: 4.5
CC: less than 0.5
CYA: approx 40-50
Temp: 80

LSI: -0.07

What has changed is that the calcium hardness test now all of a sudden starts purple.

In addition to that the brand new polished spa is getting rough after 2-3 days, i can then use a fine 180p sand paper and it gets perfectly smooth again with just one wipe without a lot of pressure. So I assume it is some form of scale that is growing on the surface ... but based on the LSI scaling should not be possible?

I read that a purple calcium test could indicate metals. Is it possible that the polishing machine somehow increased the metals in the water and this is now causing scaling issues?

PS: i should add that starting with the 5 drops of R0012 starts the test in red again.

 

[kimkats]

That had to be shocking to see! I have a call in to someone who might know!

 

[rhawke]

Yeah, the problem is this roughness (like little spikes) is coming back after 2-3 days. But only in the re-polished spots. The rest of the pool surface that wasn't touched up is smooth as can be and also the tile has zero scale. Super weird. It's now been exactly a week since they professionally repolished the few spots and I already sanded them down twice again just for the spikes/roughness to reappear 2-3 day later.

And on a side note: i also found out that my red R0014 must have been bad. I used my father in law's test kit just to be safe and his test kit measured PH at 7.8 when I measured at the same time PH at 7.5. I even swapped test blocks with reagents and my reagant was always 7.5 in both test blocks and his 7.8 in both test blocks. Mine is 6 months old, his is 2 months old.

So in reality my LSI was probably higher because the PH was higher than the test kit showed (assuming his is correct and mine was wrong). Are such variations normal? 0.3 in PH makes quite a different on CSI/LSI.

 

[JamesW]

It might be calcium sulfate or calcium silicate.

There might be metals in the water.

The Mystery of the Pointed Crystals - AQUA Magazine

Can you describe the process of polishing? Did they drain, polish and then refill?

Did the create a lot of dust during polishing and leave it in the pool?

Are you using dry acid or sulfuric acid?

 

[rhawke]

Hey James,

so they repolished individual spots in the pool with the water in it. The guy dove around and repolished spots on the steps and on the floors where it wasn't perfect. By the time he was done in the pool you could not see more than 1-2 feet, it was completely cloudy and took about 2 days to clear up with the pump running at 50 GPM for the full 48 hours.

The spa he drained completely and repolished everything. The pool builder's start up guy had by mistake poured too much acid directly into the Spa which messed up the smooth surface which is why they agreed to repolish the whole thing. After polishing, he used the pool water to fill the spa again (the pool was very full from a lot of rain so no fresh fill water was needed). I kept the valves manually in 75% Pool and 25 % pool position for those 48 hours of pump time to make sure everything gets filtered.

At this point nothing is visible to the naked eye. Even using my brand new clear goggles and going 2 inches up to the surface I can't see anything. But I feel it immediately. It feels like rough sand or tiny stones on the surface. Brushing doesn't do anything, but using the sand paper gets rid of it instantly. Only in one spot on a step right in front of a globrite light, i noticed very slightly raised bumps that had the same color as the plaster ...

And interestingly the worst area in he whole pool is the center of our Superflow 360 drain. It's the spikiest there in the center, while the 2-3 inches around the actual drain are smooth. So almost like the water movement into the drain kept the area around the drain ok but the center of the lid that is filled with plaster got the spikes ...

The only other thing that is different is that I started to use the Muriatic Acid from Home Depot called HDX 2 gallons for $13. I noticed that it fumed much more than the previous bottles I had from the pool builder. When pouring into a measuring cup, I could see the fumes cross the whole pool up to 15 feet into the air. But not sure if that is just normal ... I only used acid for 2 months now.

Sorry for this dump of information, not sure if any of this helps, but I'm trying to not leave anything out.

 

[JamesW]

I suspect that the issue is calcium silicate from the dust created by polishing.

I would suggest a scale inhibitor and keep the pH down a little bit. Brush at least twice a day and do filter cleaning as soon as possible and again in about a week.

 

[Dirk]

Can I share some advice that I regularly give, that I myself ignored when it was my turn to follow it!?

You shouldn't be doing anything to the surface yourself. Don't sand it. Or apply any other chemical or physical remedy to it. Test the water all you want. Keep the water balanced as per TFP guidelines, unless the PB has given you an alternate set of guidelines, then balance the water to his. Record the levels every time you test. Record what you use to keep the levels correct. Keep the records of results and doses safe and backed up.

It is not your job to solve this problem, it is the PB's. You can explore it all you want here at TFP, no harm no foul. But your only real job at this point is to protect your warranty. You do that by informing the PB, in writing, of the problem, and then staying out of the way. However likely or remote, you may be having all of your finish replaced at some point. Or hopefully just a lesser solution, but regardless of the extent, someone is going to have to pay for it. That should be the PB, unless he can prove that you did something to cause or otherwise inflame the problem. So don't. Be able to prove you kept the water balanced (that is always the first bone of contention) and that you did nothing to the pool except swim in it and keep it clean. Let him deal with it, get everything in writing.

Hopefully it will be a simple fix, or even if it isn't, that your PB will be a stand up guy and make it right, no matter what it takes. But if things go south, as things sometimes do when money is at stake, you want to be in good shape. Document what is going on and the exchanges between yourself and the PB, and let him take care of it.

When I was reminded of my own advice by another here, and ceased all my own plans to deal with a problem with my new pebble, and instead called the contractor... he came out, fixed the problem, no charge. Just as it is supposed to happen.

 

[rhawke]

Thanks Dirk, yeah that makes a lot of sense. I have been in contact with the PB and WetEdge applicator the entire time. I informed them of the roughness and the applicator suggested that it was simply some scale buildup, possibly from the plaster dust, that i could try to remove and most likely it would stay off.

I also asked if I should do what James suggested and keep the LSI slightly negative, but they told me to keep it as close to 0 as possible so I won't mess with it for now.

But now since this has come back 2 days after the light sanding, I am sending them another e-mail to take a look at it.

I was actually able to take good picture by the step with the globrite. It's the only location where I can see something with the naked eye and the camera got an even better picture. The color of these bumps appear to be the same as the plaster.

Does that help you guys to identify what it is?

 

[Dirk]

Wow, that is a heck of a photo. Lay a quarter or a ruler down next time, for scale. I see the bumps. No ideas about those. I also see what looks like pock marks (holes). Are there? I would consider those a defect in workmanship, or a plaster failure, depending on when they showed up. Are there many of those?

 

[JamesW]

Plaster contains a lot of silicate. Cutting, grinding or polishing creates a dust that contains a lot of silicate.

You have a lot of silicate in the water.

This will result in calcium silicate scale.

I would suggest a sequestrant that works on silica, such as Jack's Magic the Purple Stuff.

Brush frequently and clean the filter.

Dust from cutting, grinding or sanding concrete or cement should be avoided as much as possible.

 

[rhawke]

Wow, that is a heck of a photo. Lay a quarter or a ruler down next time, for scale. I see the bumps. No ideas about those. I also see what looks like pock marks (holes). Are there? I would consider those a defect in workmanship, or a plaster failure, depending on when they showed up. Are there many of those?

You mean the larger dark holes? Those are holes were the pebbles came out of the plaster. Per the applicator this cannot be avoided. While they are polishing with the machine sometimes the fast rotation from the polishing machine will pull out individual pebbles and leave these holes. They are very noticable at night when the light shines on them, not very noticable during the day.

To give you an idea of the scale: all of these pebbles are the size of 1/4 for the smaller ones up to 3/4 of an inch for the larger blue ones.

- - - Updated - - -

Plaster contains a lot of silicate. Cutting, grinding or polishing creates a dust that contains a lot of silicate.

You have a lot of silicate in the water.

This will result in calcium silicate scale.

I would suggest a sequestrant that works on silica, such as Jack's Magic the Purple Stuff.

Brush frequently and clean the filter.

Dust from cutting, grinding or sanding concrete or cement should be avoided as much as possible.

Thanks for the tips. The WetEdge applicator said they will come out again, drain the spa, get rid of the deposit, and then use a sequestrant ... he said he will research which one will work best.