There are four elements involved in the power washing process: water pressure, water flow rate, cleaning solution, and surfactant. These four things work together to give surfaces a proper cleaning. And when one of these four changes, the other three will have to compensate. For example, if cold water is used instead of hot water, you may have to use stronger chemicals or more chemicals to achieve the same results.
Power washing destroys the bond between dirt and surface. When more water is used in the power washing process, the quicker the job gets done.
Finally, operator skill can also affect the quality of the power washing. Therefore, no one should attempt to power washing any surface without the proper knowledge. If you use the wrong chemicals for one example, you could end up doing more damage to the surface instead of cleaning it.