Low Pressure

Midwestpro · Posted: Thu Jan 10, 2008 7:06 pm Post subject: Low Pressure

The major misunderstanding about power washers is that the pressure does all the cleaning. This is true to a certain degree but too much pressure can easily damage many different surfaces when it comes to exterior cleaning. The speed and cleaning efficiency in essence comes from the gallons per minute (GPM) or flow that the unit puts out. The more GPM the better and quicker a unit will clean, this together with the right cleaners and lower pressure, to eliminate the risk of damage, is an efficient plan to clean vinyl siding, wood and other surfaces around your property.

To accomplish a lower pressure for exterior cleaning it is required to change the nozzle at the end of the wand to one with a larger orifice. Nozzles are measured and stamped with a 4 digit number. The first two numbers represent the degree of the spray pattern, which most frequently range from 0 degrees or a pencil like stream up to a very wide 40 degree fan. The second two numbers signify the orifice size or simply the size of the hole that the water shoots out of. The bigger the orifice is, the less pressure is put out but at the same time the GPM are not affected. An example would be a 4010, this nozzle is a 40 degree spray pattern and a number 10 orifice. A nationally recognized “nozzle chart” is used to compare the orifice size number to the units GPM to determine how much pressure is put out.