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Pressure Washing Guide - Which psi do I need?

Date posted: 19 March 2015

When you feel that your regular garden hose is not enough to help you carry out the heavy-duty outdoor projects that require pro-like cleaning (see debris-ridden driveways and sidewalks), it’s time to consider using a pressure washer. Roll up your sleeves and get down to it with the greatest tools you could have for cleaning numerous outdoor items. Pressure washers are not only up to 50 times more powerful than a garden hose but also significantly less water-consuming (up to 80% less water than a garden hose). To get the ideal tool though, you need to know, at least the basics, so here we go.

Pressure washer types

There are electric pressure washers and petrol / diesel pressure washers. The first are quiet, light-duty models and are perfect for small cleaning projects while the latter are more powerful and range from medium-to-extra-heavy-duty models. They also provide you with more mobility (they don’t need to be plugged in to operate like you do with an electric model), but they can be used to well-ventilated areas, which may be a minus, depending on the type of cleaning project you have at hand.

What you need to know about cleaning power

The cleaning power of petrol / diesel pressure washers is measured by the machine’s GPM (Gallons Per Minute) rating* and PSI (Pounds per Square Inch)* rating. Both are important and interpreting them correctly will help you choose the most suited pressure washer for your heavy-duty cleaning project. As a general rule, ensure you go for a model that delivers the minimum PSI levels required to achieve the cleaning outcome you desire on specific surfaces or items. In other words, the PSI is the factor you should be concentrating more, when trying to determine which device to get for the duties you want it to handle.

*PSI measures the pressure of the water that the pressure washer creates, and is an indicator that will indicate the power of the water stream.

*GPM measures the volume of water the pressure washer delivers. Its rating will show you how efficiently and fast the machine will clean and rinse away debris.

Here is a first chart to begin with:

PSI Rating Models Grade/Perfect For
1300-1800 PSI Electric Motor Models (Residential) Light Duty/Delicate Jobs (e.g. grills, car washing, spot cleaning, shutter cleaning, etc.)
2000-3000 PSI Petrol / Diesel Engine Models (Residential) Heavy-duty and more frequent tasks (e.g. siding, pavement cleaning, tougher stains, etc.)
3000-4000+ PSI Petrol / Diesel Engine Models (Residential) Contractors’ very frequent, heavy-duty tasks (e.g. industrial cleaning, paint stripping, stubborn stains, mildew, concrete, siding, graffiti removal, etc.)

TIP: The cleaning power of a pressure washer is determined by multiplying the PSI x GPM rating, and the resulting number will allow you to compare models and select the one that is able to deliver all your cleaning needs. 

Based on the type of tasks a pressure washer can handle, the models range from light duty to extra heavy duty, but you may also find multi-duty models as well (petrol/diesel and electric) with various PSI levels (see detailed chart below).

Extra Heavy Duty - 3300+ PSI
Multi-Duty - 500-3000 PSI
Light Duty - 1500-1900 PSI
Heavy Duty - 2900-3200 PSI
Medium Duty - 2000-2800 PSI

Application Extra Heavy Duty Heavy Duty Multi-Duty* Medium Duty Light Duty
Car     x    
Pavement x x x x x
Stairs x x x x x
Deck / Patio x x   x x
Driveway x x   x x
Stain Removal x x      
Siding x x      
Fencing x x   x  
Garage Door x x   x x
Paint Prep x x      
Power Soaping     x    

*Multi-Duty pressure washers selected are electric models only. Most petrol/diesel powered pressure washers tick all the boxes, except paint prep.

Note: Cleaning results are also dependent on the (1) detergent you use, (2) water pressure, (3) distance between you and the surface cleaned, (4) angle of the spray fan.

Final Tips

  • Always use the right spray or nozzle setting as too much power can damage wood and other surfaces.
  • Work from ground level and not on a ladder, and use accessories (e.g. brush, spray-arm extension, etc.) to clean the house.
  • Use only the chemical recommended by the device’s manufacturer.
  • Don’t pressure wash windows as the high pressure could break them.

If you wish to hire a pressure washer, visit Best at hire your National tool hire centre. We have a wide range of pressure washers that can be Delivered to Your Door.

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