Basic help on concrete driveways?

I’m running a 2.5 GPM machine with 3100 psi. I have a little surface cleaner… SIMPSON Cleaning 80166 Universal 15-Inch Steel Surface Scrubber for Cold Water Pressure Washers, 3600 PSI…

Been down streaming my house wash mix which is 3:2 10% SH to water with a little soap and letting it sit, then using the surface cleaner.

Basically, I’m not doing jack and it’s not working. I have to move at a snail’s pace and then go back and try to get out the lines and still there are the deep green algae stains left even after the dirt is gone. Some of these driveways are old and the mold and algae is serious around here and I just can’t get them clean with what I’m using.

Due to some recent bad breaks I don’t have the $ to upgrade equipment just yet. So I was going to try muriatic acid? Is this a good or bad idea? Any other things I can do to get better results?

I guess after doing some more reading that muriatic probably is a bad idea for just cleaning driveways… good I guess if it were going to be sealed?

I’m going to wet everything down and try straight 10%SH in a pump sprayer on the nasty driveways. Then rinse really well. I’m hoping I don’t damage the lawns and stuff but not really sure how to protect everything other than lots and lots of water afterward.

DS straight 10%
Let dwell
Surface clean
Pump spray a 50/50 mix if needed afterwards


To avoid getting the lines don’t walk back and forth with with the surface cleaner. The over lapping of the tips causes cleaner “runs” which become more apparent over time.

While standing still push the surface cleaner forward, move left or right 6 inches the pull it back. Move over 6 inches again push forward. Do it all the way across then move up to a new section and repeat. You can move the cleaner faster forward and back than you could if you walked up and back. The tips over lap each other constantly making it easier for really dirty surfaces. It’s not as slow as it sounds. I got it from a guy on here years ago and it works great. Great results withZero lines.


No need to dilute with that machine. DS the Sh with some surfactant. Or go with a degegreaser. Walmart has a purple cleaner that works well.

I too started with some weak equipment this season and after having the same experience I changed my business plan. I now use the weekdays to find and book work for the weekends. I usually book between 4 and 6 jobs. Then I’ll rent a 4k 4gpm machine with a surface cleaner at 200 for the weekend. Sure, it is expensive but revenues of 1200 make it worth it for me. Going on my 5th weekend with this approach. Money and experience are pouring in and I’m building a cash reserve for next season. Good luck.


You will know if your mix is working by how it reacts with the surface. On really dirty areas (with black or green mold & mildew) I recommend putting a light coat of your mix down first. You should see it activating a bit. Then, just a minute or two later (or longer, doesn’t matter as long as it is not dry) come back with a heavier coat of your mix. You should see significant up tick in the reaction of your mix, often times with a heavy white foam forming. If that is happening, you know it’s not your mix. 1.5 to 2.5 total concentration & just a bit of surfactant, in my experience, should cut it on very dirty concrete (not talking oil residue, just dirt, mold, & mildew).

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Good deal thanks everybody. Will put it all to use.

DO NOT forget to flood the surrounding grass and such with water beforehand when you DS straight SH, if you’re worried about killing the grass. You already know to flush it after, but watering it down beforehand is just as important.

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I’ve post treated a few really funky colored ones and ones with acorn stains that remained after pre and surface cleaner. It made a noticeable difference on those

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I also use a 2.8 gpm 3200 psi Simpson. I’m a weekend warrior. Slow and steady.