Cleaning scale from pool tile
September 23, 2008 4:51 PM   Subscribe

How can I best clean hard water scale from pool tile?

We have a pool with ceramic tile at the waterline that is getting badly covered with hard water scale. How can we remove the stuff most efficiently? This page says that you can use muriatic acid in a spray bottle to help clean it, but I don't want to be spraying undiluted acid at basically eye level! What dilution can you use to loosen the stuff, and do you want to let it set or scrub immediately? Also, what tool is best to use for scrubbing? That link mentioned a putty knife, in other places I've seen a pumice stone recommended. Any other tips would be very helpful.
posted by TungstenChef to Home & Garden (5 answers total)
White vinegar. It's acetic acid, which is not poisonous and not strong enough to represent a hazard to skin, but it's strong enough to do a reasonable job on scale.

Or you can use Comet spray cleanser. The active ingredient in that one is citric acid, which also is not poisonous and not a hazard to skin.

You'd probably have to spray either of those on and let them sit for ten or fifteen seconds before trying to wipe them off, but they should do the trick.

I wouldn't want to muck around with hydrochloric acid for this, and I see no need for it.
posted by Class Goat at 5:24 PM on September 23, 2008

Will vinegar be strong enough to do the job? The scale is very thick in places and I've had to soak bathroom fixtures with a similar amount of encrustation for hours or even overnight to get it off.
posted by TungstenChef at 5:55 PM on September 23, 2008

There is a brick by the name of "Soft Red" that is available in the South that I use as a pumice stone to scour away the scale in my toilet bowl. It does not scratch the porcelain. I stopped by the local brickyard and was able to get a broken off part of a brick for free.

Pumice Brick I imagine would work as well. Try it on a inconspicuous spot on your tile. This is a chemical free way to clean the pool tiles.
posted by JujuB at 6:04 PM on September 23, 2008

If the scale is carbonate (calcium or magnesium carbonate, probably) then either vinegar - acetic acid - or muriatic acid will make it fizz and that is the indicator you need. I have had excellent results removing carbonate scale from both dishes and tile with citric acid. Citric acid can be had in bulk at places like When you are mixing it up to spray it, sometimes it helps to use a little dish soap - like a drop per liter - to reduce the solution's surface tension thereby allowing it to penetrate better.

If the scale is tartaric then it's likely to require mechanical removal.
posted by jet_silver at 8:51 AM on September 24, 2008

To follow up, I first tried vinegar but it was too weak to deal with the serious amount of scale I had (over 1mm thick in places). So I donned hand and eye protection and attacked it with undiluted muriatic acid in a spray bottle. That did the trick, it fizzed vigorously when it hit the scale which removed some of it outright and made the rest more brittle and easier to scrape. I picked up a pumice stone and that worked well to scour off the light buildup. The heavy buildup was too much for my putty knife (too flexible), so I sacrificed a cheap wood chisel to the cause. The spray bottle turned out to be very easy to control too, I didn't have any problems with acid going in places I didn't want it to.
posted by TungstenChef at 1:19 PM on September 26, 2008

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