Use at a distance. I've only ever used one on a filthy MTB before putting it in the car at a trail centre. I'd never use one otherwise. A hose is usually enough pressure to wash off the bad stuff, before soap and a sponge.
A hose is easily enough.
Just a point of health.
Using water from a water butt for pressure washing carries a high Llegionella infection risk.
So connect to your outside tap ,i know...
If your bike is not very dirty.