This is a brief of Water Quality which is used in pressure washers, water blasters, and UHP Water Jetting equipment. I compiled information from equipment manufacturers directly or from their published data.
When removing corrosion or coatings from projects, the contractor should use the best quality of water which is available within the constraints of the project. The better quality of water, the longer the the pumps will perform. For a paint or coatings re-application, the revealed substrate is often tested for residual contaminants- such as residual oil (water-break or fluorescent), or electrolytes (salts). The measurement on the surface should be below the limits of the project contractual requirements. In my opinion, the contractor truly does not want to add contaminants to the substrate.
Should you heat the water? That depends. Generally hot water will dissolve more “salts” than cold water. However, during the pump cycle the water is compressed and thus heated. You don’t want to use water that is so hot that bubble will form. So just be careful. Equipment manufacturers might place a limit on the upper temperature of the input water.
For specific details-see the paper Quality of Water in the library.