Tempting though it may be to use hot water with your pressure washer, Ryobi cautions against using hot water. In the user manuals for several of its pressure washers, it states to “NEVER use hot water or water from pools, lakes, etc.” In fact, most Ryobi pressure washers are listed specifically as cold water at Home Depot and other retailers. Though it doesn’t explain why that’s a bad idea, it’s always best to follow the manual. Particularly when it comes to extreme temperatures and using a piece of equipment like a pressure washer.
Pressure washer manufacturer Hotsy also cautions against using water that’s too hot, explaining that some hardware is not designed for it. And that using water that’s significantly hotter than the system is intended to handle could lead to damage like overheating or melted seals. This can lead to the pressure washer leaking at one or more connection points, losing pressure, or ceasing to function entirely. So unless you know for certain that the washer can handle hot water (again, check the manual first), keep things cold.