Pressure Washers, Steamers & Damage to a Roof
I have been employed in the cleaning equipment industry for 16 years and have used, tested and sold hundreds of pieces of equipment. I am very familiar with hot water pressure washers and steamers and as a company we offer both types of equipment and each have advantages and disadvantages for certain applications. Unfortunately, in our industry terms often mean different things to different people and this causes widespread confusion and erroneous information. The one application most often abused in roof steaming is Pressurized Spray. It should never be used on an asphalt roof to melt an ice dam.
A hot water pressure washer typically operates at outlet temperatures between 150F and 250F and has a nozzle that sprays water in order to create impact force to clean, this impact will damage a roof. This type of nozzle is never used on a steamer and should never be used on a roof.
Many people will call a hot water pressure washer a steamer. But if it is spraying through a nozzle, like above, it is a pressure washer and should not be used on an asphalt roof.
At about 250ºF to 260ºF the spray changes. At that point, there is enough energy in the water to change it to steam. The steam, because it is now a vapor and occupying much more space, needs to be directed. The steam nozzle is stepped internally and directs the large volume of gentle spray coming from the steamer. This melts a path with heat and does not create the damage associated with even low pressure from a pressure washer spray.
This is the type of nozzle that should be used on a roof: