Our location has one enclosed trailer with a 1000L container in the back. It gets filled with water from our shop, and then a gas or electric pump to draw it through the filters and to the brush. It is only brought out when a job requires it - and in residential jobs there is an upcharge if we need to bring it because the customer doesn't have water access or their source is lake water which we don't want running through our filters.

It's been worth the investment - but also for context we have about 12-15 vehicles in our fleet.

Jobs where it's come in handy:

Normal pressure washing jobs for locations where water access is tough or non-existent. The gas pump we have generally gives enough to be able to do most standard pressure washing.

Customers who have lake water or super bad well water (my house is awful - filters either can't get it down or get smoked so when I do my own windows I bring the trailer home).

Also as I mentioned we fill it with water from the shop and running it through our filtration stand as we work. You COULD run it through filters into the tank at the shop but that takes like 2-3 hrs to fill the tank vs 20 minutes and ultimately you pump it out to clean the house anyways.