Scale Under Spillover

BoilerSim

Gold Supporter
Apr 22, 2019
28
Winter Garden, FL
Hey all. I’ve been dealing with what I assume is scale buildup under our granite spillover for a while now. I had the builder clean it up about a month ago when they fixed the grout line, but it is back with a vengeance. Any ideas on how to clean it up and maybe prevent it from recurring? My CSI is almost always between -0.3 and 0.05, so I don’t think my water chemistry is at fault. Tried to knock it out with a pumice stone today, which helped a bit, but not nearly enough. I’ve attached a couple pics below. Thanks!

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JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,767
Tucson, AZ
That looks more like efflorescence. I’m guessing the granite is not sealed nor is the grout? Water from the spa is seeping in between the granite slab and the concrete wall through the mortar bed used to hold the granite down. The slow weeping of moisture down the tile is leaving the scale deposit. The only fix is to seal the granite, and tile grout around and under the spillover.
 
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BoilerSim

Gold Supporter
Apr 22, 2019
28
Winter Garden, FL
That looks more like efflorescence. I’m guessing the granite is not sealed nor is the grout? Water from the spa is seeping in between the granite slab and the concrete wall through the mortar bed used to hold the granite down. The slow weeping of moisture down the tile is leaving the scale deposit. The only fix is to seal the granite, and tile grout around and under the spillover.
That makes sense. Based upon the way our project went, I highly doubt the builder sealed the grout, so I’m sure that’s what it is. I think I can figure out how to do that. How would you suggest removing the scale before I seal it? Don’t want to seal the scale in.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,767
Tucson, AZ
Mask off the granite (as it is calcium and magnesium carbonate) and then use a dilute acid spray and stiff Tampico brush (or nylon if you can’t find Tampico). You can also use a pumice stone but be GENTLE on the tile or else you’ll scratch the glaze. BioDex sells a tile scale remover that’s thick like toilet bowl cleaner BUT it contains hydrofluoric acid which is extremely dangerous to mess with. I’d recommend the low tech approach first before you go nuclear with the BioDex.

After that, I suggest using either DryTreat 40sk or DuPont StoneTech sealer on the granite slab. As for the grout, shop around and see what kind of grout sealers are available. You’ll want to seal both sides of the spillway. Do an inconspicuous test on the grout sealer to see how much it changes the color/tone of the grout. If there’s a deep change in tone, you might have to seal everywhere to avoid having different shades of grout. The best way to grout pool tile is with an epoxy based grout but you rarely find pool builders willing to use it because it costs more and requires a bit more skill to work with over cementitious grouts.
 
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BoilerSim

Gold Supporter
Apr 22, 2019
28
Winter Garden, FL
Just wanted to share that while I’ve not been able to address this myself yet, I did approach the builder about it. They sent a tech out to clean it up, who suggested we just use Jack’s Magic Purple Stuff and it won’t happen anymore. I think I know the answer to this, but that’s a complete cop out answer and that won’t address the issue, correct?
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,767
Tucson, AZ
If it’s efflorescence from water infiltration then no, it won’t. Might slow it down a bit but it will not stop it. The stone needs to be sealed against water infiltration.