How to remove stubborn Efflorescence build up on rocks?

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Dixit

0
Jul 16, 2012
123
Duluth, GA (ATL)
I just took ownership of this house about 2mo ago and pool was in OK shape, had to redo a few things, ended up converting it to Salt water, fixed the LX400 heater, fixed the Caretaker 99 5way valve, replaced the cracked CL580 filter tank bottom, replaced the seals on the motors, the list goes on.....

During the drain/refill (350+ CYA reading, tested 3x on my K2006), we ended up also acid washing the plaster. There is an area around the Spa side where the rocks have excessive Efflorescence (thats what I think it is, doesnt look like calcium to me, unless Im wrong) build up. Normally Muriatic acid mixed down to 4:1, 3:1, 2:1 (whatever you need) will take care of that and burn it off. Ive done it about 4x on this rock wall and only got it about 25% cleaned, the scale on it seems so thick that its not going to come off that easily or get burned off by MA. Ive even done 100% MA (at 31.45%) on it and it still doesnt help any. Im afraid to take a brush to it as brushing it back and forth with MA is going to sling/fling MA all over the place including me.

Here some pictures of the main trouble spot (will post links instead of embedding them since they are larger resolution, wanted to keep the detail in the pictures). And PS, its wet because I just tried it again by pouring about of MA straight out of the jug to see if it would eat more of it, it didnt seem to make much difference.

This is the overall area, you can see the large white spot near the base of the spa rock wall and the pool stone coping.
http://img836.imageshack.us/img836/8969 ... cence1.jpg

This is a closeup of that large white area, that one rock has I would say a good 1/16" to maybe 1/8" build up on there, some of the gaps between the rocks have even more buildup.
http://img51.imageshack.us/img51/8494/e ... cence2.jpg

This is some other areas on that same wall but not as bad as the one above.
http://img607.imageshack.us/img607/6580 ... cence3.jpg
 
Well, that is a bunch of it, for sure. Since you don't have grout to worry about, I wouldn't be afraid to put 100% muriatic on it multiple times until you got it off. Does the muriatic foam up when applied?

The only other avenue I can think of is wire cup brush on an angle grinder but even that may not be aggressive enough. They make some pretty coarse attachments for an angle grinder and I think that's what it may take. Probably even scuff the rocks a little but I don't think it would show.
 
It definitely foams up when I put 100% MA on it. I dont think anything metal bristle brush is going to work since MA is just going to eat/corrode those metal based brushes. And then using nylon or something softer probably isnt going to do anything to help pull it off.

Well just wanted to make sure that basically using MA isnt going to solve this and will have to go to more extreme levels like you suggested of litterally scraping it off by hand or using some form of power tools.

Dixit
 
Thats a good idea. I have a high end Rigid one, its massive. It puts out I believe 3300psi. Might give that a shot first to see if it will knock it off. May end up putting a tarp/cover over that area of the pool first, dont need all that Crud ending up in the pool.

Dixit
 
Yea you have to be careful there. I did that once and it put a hole through concrete driveway. Mine has these different nozzels I can put on the wand. I no longer use that jet one. It really should never be used unless your intent is to put holes into something and really intend on breaking into something or something apart. The flat head should work in most causes if you get close enough and crank it up.

Im going to break this bad boy out maybe tomorrow and see what happens. Need to rig up a tarp over the pool in that area to help catch all the bits of Efflorescence that will be flying all over the place. Last thing I need is to mess up my absolutely crystal clear pool water now. Just got finished balancing it all out, BBB method was done about 1week ago, water chem is perfect.

Dixit
 
For anyone who was wondering how this is going. I managed to breakout the 3300psi Rigid Power washer. Put the 15degree flat nozzle on it (basically the smallest flat spray I can use before going to a 0degree pinhole spray) and I sprayed this area pretty hard at only 1" away from the rocks. And I managed to get about 50-60% off but could not get anymore of it off. Even trying to go at it from different angles to simulate scraping it off.
This is basically how much got cleaned if you compare this image to the 2nd link in the first post.
http://img52.imageshack.us/img52/2692/e ... eaned1.jpg

This is the other area which really dodnt seem to have much if anything come off. This link is in comparison to the third one in the first post.
http://img850.imageshack.us/img850/2960 ... eaned2.jpg

Since this was cleaned, I hit it again with 100% MA (no mixing it down) now that it has some new layers exposed after power washing, so Im going to try that a few times to see if that helps. But initial MA treatment didnt seem to do much. So only option now left is to probably break out the chisel and start pecking away at it. Maybe put a bit on my dremel and just grind it off as there are many nooks and crannies to hit.

Dixit
 
Hey, Dixit - How'd this exercise turn out? I'm attacking a similar problem, but it's on my glazed tile. I'm able to chip the efflorescence/scale off w/ a putty knife, but it's tedious. I know the muriatic acid worked some, but did you find anything better?

Thanks!
 

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Its basically gone off the surface. I hit it with the 3000psi pressure washer about 3 times and each time in the middle hit it with the MA straight out of the bottle. Eventually got it all off, except the where its in the middle of the stones. Almost impossible to get it off there, don't want to hit that with the pressure washer in fear that its just going to eat/destroy the edges of the rock, 3000psi is a lot of pressure.

Dixit
 
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