Surface Cleaner Stripes on Concrete

When cleaning flat concrete, vertical lines can occur sometimes referred to as "tiger stripes". There are 4 major reason why this can happen and we will cover them here from the most to the least likely.

1. Surface Cleaner is Underpowered

Many times, technicians will use surface cleaners larger than their pressure washer can push. The commonly accepted practice is 4" for every GPM. This means, if you are using a 4 GPM pressure washer, you want to use no more than a 16" surface cleaner. While 4 GPM will work with a 20", it will be underpowered. 

To resolve this issue, change your surface cleaner. In the meantime, move slower to allow the surface cleaner more cleaning time. If striping has occurred, clean the surface again in the opposite direction slowly. So instead of up and down, you will be cleaning from left to right.

2. Technician moving too fast with the surface cleaner

Technicians moving too fast with a surface cleaner can cause circular rings or striping. To resolve any lines made, go back over the surface in the opposite direction slower. 

3. Clogged nozzles in the surface cleaner

Clogged nozzles will happen from time to time. Debri in the water source will put a make its way to the orifice of the surface cleaner nozzle causing the surface cleaner to shake or vibrate. Remove the nozzle, clear the debris and reclean the surface in the opposite direction.

4. Overlapping lines with surface cleaner

Many people treat surface cleaning like vacuuming. Meaning they will try to aline the surface cleaner on the previous line they just cleaned. High pressure washing actually removes a small amount of concrete from the surface. Overlapping directly over the same edge that was just cleaned can remove an additional layer of concrete effectively etching the concrete. Try not to clean directly over the same clean line, instead overlap by 2-3 inches. To resolve any lines made, go back over the surface in the opposite direction slowly.