On Sat, 11 Jul 2009 22:25:19 -0400, Some Guy wrote:


I'm looking at a few gasoline-powered pressure washers.

Naturally, the typical specs a

a) the hp rating of the engine
b) the gpm
c) the psi

So my main question is - are these numbers fudged, or have a wide
accuracy range?

Yes, expect a lot of fudging.


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

It depends greatly on the type of work and the quantity of it.

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".

Sorry but what you want to wash is a critical part of the
choice. A large sledge hammer is good for splitting logs, but it is
not very good at cutting diamonds.


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).

Depends. Some things clean up best with more volume and less
pressure and others with more pressure and less volume. In both cases
it generally is faster - better with more volume and pressure.