On Sat, 1 Nov 2008 17:12:34 -0700 (PDT),
wrote:

On Nov 1, 12:42*pm, wrote:
I understand that GPM can be as important or more important than PSI
for "getting work done". *So, I'd like as high a GPM as possible,
obviously. *I'd be using the pressure washer for occasional home use
and occasional semi-pro use for handyman/odd jobs.

But I'm concerned about source water flow. *I'm on city water, but I
just checked an inside line and an outside hose, and I'm getting 4 GPM
max, maybe 3.5 GPM. *Does that definitely rule out a 4 GPM machine?
I'm concerned about cavitation in the pump.

I doubt if you will have a problem. First the numbers listed are
usually .... shall we say optimistic. Second the power washer will
be able to "pull" some additional water than the water flow you
measured. In theory it can pull a 32 foot column of water before it
quits, in practice it is less, but still significant.

Although power washer may be able to pull some vacuum they are
designed to be force fed. Any restriction of the supply is not a good
thing.