On Jul 11, 9:25 pm, Some Guy wrote:
I'm looking at a few gasoline-powered pressure washers.


What is the minumum rating (in terms of gpm and /or psi) that make it
worth while to actually buy one of these things?

The range I see are from 2 to 4 GPM, and roughly 2000 to 4000 psi.
Engine HP from 6 to 13.

Your answer should not include "it depends on what you want to wash".

I want to know if a washer that does 2 gpm @ 2000 psi has only half the
"cleaning power" as one that can do 4 gpm at 4000 psi (ie does the
cleaning power scale linearly with these numbers, or geometrically or
exponentially).

The numbers are real, but they are also somewhat meaningless other than
rough comparison. While you don't want to hear "it depends", in actual use,
it does. The rating figure is for the water coming out of the tip at close
range. In actual use, the 2000 psi unit held at a food or two is giving the
same pressure at the 4000 psi unit held a longer distance, and the object of
being cleaned in receiving far less than the rated numbers.

My experience is limited to a 2500 psi model and I've never wanted more,
either at home or at the shop. OTOH, if I wad dong heavy cleaning of power
plants every day, I'd go with bigger.