Hi this is my first post on the forum, I’ve been enjoying reading for some time. My question is about cleaning concrete driveways that are really white looking. We’ve had a problem with these etching the concrete where the surface cleaner overlaps. It is not dirty it is definitely etching. We tried turning the pressure way down and it looked ok when wet, but after it dried there were faint lines where it overlapped. Why is this happening? Is this just really soft concrete? Is there a safe way to wash this stuff?
I’m not an expert by far, so this is just a guess, but you might want to change the nozzle size on your surface cleaner. As far as if the concrete is just realy soft, I don’t know.
Ron or Micah are the guys to ask.
You need to match the tips on the surface cleaner to the GPM of your pressure washer. Since most surface cleaners have two nozzles, you would divide your pressure washer’s output GPM by 2. So if you’re using a 4GPM pressure washer, you would want to use 1502 or 2502 nozzles. That’s 15 or 25 degrees at 02 GPM.
If you’re running the wrong size tips, you will have overlapping and it will leave stripes. On very rare occasion you will have this on concrete even if you have the correct nozzles. This is generally because the concrete was not installed properly or the mix is wrong. If the concrete is new, I never use a surface cleaner on it until it is 45 days old or so - long enough to cure.
Sometimes if the striping will just not go away, no matter what you try, you can spray a light mist of sodium hypochlorite on the concrete. This generally blends everything together. I’ve never done this myself, just heard of it being done with success.
Thanks for the reply Micah. I’ll check the tips. Most concrete is not an issue, just this really white looking stuff. pretty sure its over 45 days old.