First time for me seeing this

Doing some flat work for one of my clients and I’m getting these 2 streaks right down the middle. Havnt seen any concrete I’ve done before do this. The homeowner says it is fine becuase it looks way better than it did. But I think it looks bad.

I’m using a 18 in surface cleaner and 4200 psi pw.

What nozzles are you using? Are you pretreating with 3%?

I’m confused by the pic, is the lower part of your pic where you cleaned and the black looking area just not done yet? The streaks are there in both the semi-clean and dirty sections. I say semi-clean because nowhere in that pic am I seeing 100% clean concrete.

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Also, the psi rating on your pressure washer doesn’t mean squat, what nozzles are you using and what’s the gpm rating on your machine?

The basic ones that came with my surface cleaner. And yes post and pre.

That’s just how the concrete was, the farther concrete is older I’m guessing, the closer more white concrete is newer.

4gpm and nozzles I havnt changed.

Ok you need to have proper nozzles for your 4/4 machine, dial it down to about 3000psi or less.

Thank you very much! I will go buy some nozzles now!

Just tested the new ones out at home, and they are sooo much better. I will post pic of the job tomorrow when I go back. Thank you all for the help!

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2500 or 4000 are your only options with 4 gpm.

Good point.

It’s just still dirty. That’s all. Doesn’t really seem like you pre or post treated. Go slower, especially with a 4 gpm