The single most important thing that you would need during pressure washing would be a steady supply of water, and much of this fluid will be acquired from the people that have hired you in the first place at any given point in time. A big part of the reason why that is the case has to do with the fact that it can be really cost prohibitive to transport this water yourself, and trying to make it so that you can access it at the site of your work will be far more convenient in some way, shape or form.
That said, you can’t just connect your Dickinson pressure washing rig directly to the water mains. Instead, you need to connect a hose from the house to a buffer tank for pressure washing. That allows you to fill the buffer tank up and then start using water. Using the direct mainline of water is a really problematic thing to take part in, since it can damage your plumbing in wide range of ways all of which would be expensive to repair.
In order to connect the hose, you need to attach both ends of it with clips. These clips will secure it to the house water supply on one end and the buffer tank on the other. Make sure that there are no kinks or twists in the hose otherwise the water would take much longer to fill up than it needs to. Keeping the hose straight and devoid of any obstructions is something that can allow you to fill up the tank in a far shorter period of time all in all.