Don't have it handy to know the number but the stream appears to be less than 2mm diameter.

The car wash pressure washer does indeed operate at high pressure but the combination of nozzle size and spray pattern combined with distance to the work piece means the pressure at the surface cleans but doesn't damage. You're dead on right about professional washing equipment. Commercial washers have perhaps two orders of magnitude higher flow rate so the work surface is flooded at a safer pressure level because of distance to the surface. A home pressure washer at lower volume encourages the user to get closer to get more water on the piece. At 2" or less distance the situation probably becomes bothersome. One can caution another not to get so close and to use a fan nozzle or adjust to a fan pattern, but temptation is what it is and the finish will often be affected. This is probably one of those "trained professional, do not attempt at home" moments.

Charlie

 

Wow, I don't think I've ever seen such a discussion on pressure washers that has been so negative! With any common sense at all, there is no way to damage your paint with one of these little 1500psi units at all. I am a partner in a car wash in my home town - low pressure (prior to triggering) is 700 psi. Triggered pressure is 2500. Never had an issue with anyone's paint coming off. I sold pressure washers in my paint store for 9 years and I was a painter before that - I've had some experience with them. As an example, I had the opportunity to use a 2500 psi unit on an old house 3 weeks ago, and full pressure on 100-year-old wood and paint using a 20 degree fan tip gave it a good cleaning. I had to use a zero-degree rotating tip to take off the old house paint. There are stationary zero-degree tips where yes, you can write your name in concrete and cut a board in half, but no one would use these on their car unless stripping rust from an old frame - there's no fan! The fan widths provided with most common washers will be a tight 20-degree for heavy cleaning, a 40-degree for rinsing, and a flood tip for using with a siphon hose/soap unit. None of those tips, even with a larger 3500 psi unit, would harm anyone's paint unless they were rightupclose on the surface, which none of us would do. None of these tips at 12-18 inches from the car at pressures well above what is being asked about here will do any damage to the paint.

EXAMPLE: For cleaning WOOD, here is the recommended distance from the surface you need to be at for a good cleaning at the stated pressures, 20-degree fan. Our paints are far more durable than plain wood fibers.

PSI Rating Nozzle Distance:
2000 or less 8 in. to 18 in.
2000 to 3000 12 in. to 24 in.
3000 or more 18 in. to 36 in.