pressure washer to draw from a tank??

[HCJtractor]

I tried my pressure washer hooked directly to my tank today. I was always afraid to because the manual stated it required a certain psi and flow. I had been using it with an inline pump but that was a pain. It worked just fine, and never seemed to be struggling. I washed fertilizer residue from my tractor for 30 minutes. My washer is a Home Depot version with a Honda engine.