Pressure Washer Nozzles
A pressure washer usually comes with a varieties of nozzles, color coded to indicate the spray angle. (Red 0 degrees, Yellow 15 degrees, Green 25 degrees, and Black (soap) 40 degrees). Each nozzle has a orifice sized to produce a certain PSI with the rated GPM of the pressure washer. The Pressure Pro has size “09” orifice nozzles, which at 8 GPM will produce approximate 3000 PSI. This is a different number than the spray angle that is color coded, a size “09” green 25 degree tip with produce the same PSI as a yellow 15 degree tip (in this case 3000 PSI).
How to reduce pressure
We are going to “soft wash” the house, so 3000 PSI is far too much pressure to use for our purpose. We want to use between 800 – 1200 PSI to wash the home, so how do we accomplish this? One way is to reduce the throttle of the engine, this will reduce the RPM that the pump is running at and also reduce the PSI. However this will also reduce the GPM of the pressure washer which will make the washer much less effective. The best way to lower the PSI and maintain the rated GPM is to use tips that are a larger sized than the ones designed for the pressure washer. We will use the chart below to determine the right sized tip to achieve soft washing with a 3000 PSI 8 GPM pressure washer.
Choosing the correct size nozzles
Looking at the Chart we see how much pressure a size “09” nozzle will produce at various GPM. Following the chart from the left, we see at 8 GPM a size “09” nozzle will produce 3000 PSI. This is our default tip that comes with the Pressure Pro. Going to the “700 PSI” column will go down until we see a GPM close to 8 GPM. (In this case 8.37 GPM) A size “20” tip will produce 700 PSI at 8 GPM, this is the size of nozzles we want for our Pressure Pro to “soft wash” the home. You will have to use the chart to find the appropriate nozzles for your size pressure washer based on your rated GPM. You will use the higher pressure 700 PSI nozzles to wash brick up or wood close, to spray metal gutters with more pressure to remove mold, or to more easily remove cobwebs and debris from high distances. With 8 GPM it is possible to rinse the home with very low pressure nozzles, less than 100 PSI. From the chart below we can see that a size 60 nozzle produces 100 PSI at 9.49 GPM so with a 8 GPM machine we can rinse the home using low pressure 60 orifice nozzles that we also use for soap.