In the past ( no longer used because of California regulations ) my company has used diesel fuel heated pressure washers. Basically, a flame is run through a coil. No boiling or steam. It does get the water extremely hot, though. The pressure is created by a pump. Our current pressure washers use electric heaters to cook that water. We used to have a few, industrial
http://www.karcher-usa.com models. But I'm not sure what the current manufacturer is. Our machines are about pressure with heated soapy water. Not like the olden days where it was actually a steam cleaner.
