Pressure washing not removing all of the stains


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Old 11-26-18, 03:28 PM
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Pressure washing not removing all of the stains

Hi everyone,

Our driveway and front walkway at our house here in Florida get a lot of what i assume is some sort of mildew over the course of the year. I end up pressure washing it every few years, and i really need to protect it with something to make cleaning easier so i'm not blasting the concrete down to the aggregate, which is the direction i seem to be headed. Before i do that, though, my front walkway has proved especially problematic with these remain black spots. Neither bleach nor vinegar has been able to lift it up. It's definitely not black stone in the concrete.

I'm open to ideas if anyone has any.


Thanks,

Steve
 
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Old 11-26-18, 03:57 PM
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My concrete pool deck gets like that.
I use a revolving turbo tip nozzle but it does erode the concrete every time it's done.
Depot used to carry them. Lowes and Harbor Freight should have them.

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Old 11-26-18, 05:14 PM
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Pressure washer surface cleaner, amazing results!

https://www.doityourself.com/forum/a...1&d=1543281244
 
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Old 11-26-18, 08:54 PM
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What is that DeWalt thing in the photo? Enlarging it just blurs.
 
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Old 11-27-18, 12:15 AM
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Surface cleaner for your pressure washer.

https://www.homedepot.com/p/DEWALT-3...E&gclsrc=aw.ds

My 12 year old paver patio was really dirty as well as the steps. I've cleansed with power washer in the past but it would leave streaks and the patio with all the sand joints didnt seem like it would be a lot of fun.

This think did am amazing job and with no streaking and I actually stayed dry!
 
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Old 11-27-18, 03:48 AM
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If you spray the concrete down with bleach water first it won't take as much pressure washing to get rid of the mildew.
 
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Old 11-27-18, 06:56 AM
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I may not have been clear in my original post about when i applied the bleach and vinegar, but both were applied prior to pressure washing—and not at the same time. Neither made any sort of difference, nor did the "concrete cleaner" that i had purchased from Lowes.

I've thought about trying one of those circular/orbital scrubbers, but haven't really read any great reviews on them. Plus, i've got a lot of concrete to clean and those seem kind of small.

I've had a turbo nozzle before, but it tends to leave the circular patterns too much, which after looking at the Dewalt piece, is a distinct possibility with that as well.
 
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Old 11-27-18, 07:07 AM
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How strong a bleach solution did you use? did you rinse it off before it dried?
 
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Old 11-27-18, 07:10 AM
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I don't quite remember the mixture, but it was the heavy duty clorox concentrate from Home depot. Mixed it as directed. I don't believe i rinsed it off before it dried.
 
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Old 11-27-18, 10:57 AM
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A lot of cleaning agents don't help much if you allow them to dry on the substrate. The cleaner and grime tend to get re stuck. I like to apply the cleaner, let it set but not dry and then pressure wash.
 
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Old 11-27-18, 12:35 PM
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Plus, i've got a lot of concrete to clean and those seem kind of small.
Actually the amount of time it took to do the 24x24 patio and walkway was minimal, much faster than attempting to use any type of hand wand attachment and no swirly marks.

Well worth the $50 investment for the lightly used one off eBay.

Next year it's the entire driveway!
 
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Old 12-02-18, 09:03 AM
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pres wshing wears out conc - too strong & you'll eat the paste which holds the coarse aggregate together,,, all we ever use is 3,500/4,000 psi w/turbo nozzle HOWEVER that's a prep for applying polymer-modified cementitious overlays & does require a soft touch
IF we just clean, dawn works good as anything else UNLESS you use muriatic acid:water 1:8 mix
 
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Old 05-18-20, 10:00 AM
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What strength of bleach do you use. How do you keep it off of yourself (wind is always blowing)
 
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Old 05-18-20, 10:40 AM
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I usually cut the bleach in half with water although I think some of the off brands are already cut.
I generally apply the bleach solution with a pump up garden sprayer .... and I wear old clothes.
 
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Old 05-18-20, 01:42 PM
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Thanks for the reply, so the 50/50 bleach is better than then the commercial products? So I guess the clothes will be old clothes will be old after the bleach.

Thanks for the reply
 
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Old 05-18-20, 02:08 PM
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Sorry, but I should have asked, What pump sprayer do you use. There seems to be talk about having t have a special sprayer for bleach. Thanks again for your reply
 
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Old 05-19-20, 03:19 AM
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I don't know if bleach is better than the commercially prepared/packaged cleaners but it's cheaper. When bleach alone isn't enough I'll add TSP to the mix.

I've always used a pump up garden sprayer to apply the bleach [and TSP] mix. I've some heard folks say it needs to be dedicated for bleach only but I've never had any issues although I do always rinse it well when I'm done.
 
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Old 05-19-20, 06:59 AM
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Thanks for your reply, I have used TSP before it is pretty HOT stuff for sure.

When you use bleach do you have to wet it until it runs off the wall, oh yes I a spraying on sand stone and line stone rock house walls. Thanks again
 
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Old 05-19-20, 07:03 AM
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It all depends. Sometimes a light mist is enough but other times you need to flood the surface. Always rinse before it dries.
 
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Old 05-19-20, 07:50 AM
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Thanks very much for the replies. So rinsing before it dries is a problem in the hot weather especially in course rock and stone, but it does make sense.

 
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Old 05-19-20, 11:13 AM
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It rinses easier while still damp, if it dries it takes more effort plus once the cleaner dries the unrinsed dirt starts to take hold again.
 
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Old 05-19-20, 01:13 PM
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Thanks for the reply. I appreciate it.
 
 

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