Black Streaks , after using sidewalk cleaner

G

Guerrilla

New Member
I have noticed light black streaks, that appear in the area of a white concrete (mostly slanted driveways) after I have just cleaned it, It appears to be the width of my side walk cleaner. I have tried to go back over them, but they seem to stay. I have tried new noozles when I started to notice them, and tried to see if the hot water was the cause, and used only cold. but they are still there. and they seem to only appear on slanted surfaces.

Brian
 
B

Barry M

New Member
Pictures of Black Streaks?

Pics would help. I'm guessing you might be talking about zebra stripes where you are overlapping each pass. Are maybe you are describing swirl marks in either case try slowing down, see if that helps.

What size surface cleaner are you using? What GPM is your pressure washer?
 
G

Guerrilla

New Member
It's 19 inches, and the pump is 5.5 gpm. and I have tried going slow. another thing I have noticed is that I think they appear only on drives that are very dirty. but I do go over my passes. I go down, then back up. and repeat if it needs to be done again. then I slide over. and do the same thing. I though maybe that the dirt and debris was seattling back down and driing , so I have tried rinsing, but not even with a sharp (yellow) nozzle, will remove them. I will take some pictures, and you can let me know. Im also open to any suggestions.
 
J

john orr

New Member
I'm guessing that the "stripes" occurred where you have overlapped passes. What happens is that you have actually cleaned that area twice and abraded the surface - actually removing some of the cream form the concrete. A few things to try: overlap as little as possible, increase the size of the tips to reduce the pressure; move as fast as possible; clean in the direction of the "grain" (concrete is usually brushed side-to-side) of the concrete; apply a bleach solution after cleaning or possibly oxalic acid.
 
G

Guerrilla

New Member
5.5 gpm/ 2000 psi

I have a pump thats output is 5.5 gpm, and have the unloader turned to 2000 psi. I have also tried going with the grain (side to side, instead of up and down) and they appeard side to side. I have never had this problem , until recently. and why only on surfaces that are angled? I 'm going to lower the psi tommorow. I though at first that maybe the bristles were leaving the thick light black marks, or the heat was to hot, and cooking the ground.
 
G

Guerrilla

New Member
In-line with arm

I did , they are inline with the arm.

would cleaning with the side walk cleaner, on drives that are heavely dirty, then appling cleaner . and running the side walk cleaner over it again, have anything to do with them
 
D

DAFF

New Member
Sorry about the GPM read the thread incorectly!!! You mentioned about the tips. Did you replace them??? I'm thinking a piece of dirt might be lodged in the orfice or an impropper fan width in respect to the ground to tip. Try flipping the unit over and stopping the arms in spinning, this will allow you to inspect the fans and check for flow. A fan might of tuned and is running a little bit of parallel.

My self I use a regular 6' wand with a slight arch to it. With a 2520 tip and backpull while cleaning. Never thought the $500.00 surface cleaner would be worth the cash. I might be wrong. Do these surface cleaners bight into the paper expansion joints in the concrete???Let us know.

DAFF
 
P

piedmontpw276

New Member
Hi, did you check you wheels/castors? Sometimes the bearings get fouled slowing the wheel(s) and causing a slight drag - this can create black lines/streaks. If its the entire width of your machine check where you are getting your water. The same bacteria that causes iron stains reacts with lime and darken conrete.

Donna
Piedmont Pressure Washing
 
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