Thinking About Buying a Pressure Washer?

Recently, many of South Africa’s luckier dads would, no doubt, have been delighted by the gift of a pressure washer on Father’s Day. It is a gift that will ease the burden of cleaning the family car and will be sure to delight mum when her hubby uses it to clean the driveway and perhaps clear the oil stains from the garage floor. Though highly effective, the technology underlying these invaluable devices is comparatively simple.

At the heart of these machines is a pump. The primary purpose of a pump is to produce a flow of liquid. A pipeline system will often utilise several of these units to convey fluids over considerable distances. However, in a pressure washer, the pump must provide more than just the means to move the water. It has a dual function in practice, being responsible for both the rate at which the water emerges from the machine’s nozzle and the pressure behind it. It is usual to express these operating parameters in gallons per minute (GPM) and pounds per square inch (psi), respectively, rather than using their metric equivalents. These two values are inversely related. As one increases, the other will decrease proportionately.

In its simplest form, a pressure washer is a portable machine consisting of a water storage tank, a sufficiently powerful pump and a handheld lance or wand to direct the water jet. An electric motor drives the pump and may draw its power from a built-in battery or a car’s battery via a suitable cable. Other variants may use water from a stand tap and obtain their power from the mains supply, while a small petrol engine may drive some units. A machine operating at between 1 300 and 1 700 psi with an output of around 2,5 GPM should be sufficient for most domestic tasks.

For car cleaning, a pressure washer with the above performance characteristics will have sufficient strength to strip away the dirt and generate a flow rate that ensures rinsing will remove any residual loose particles or cleaning product to guarantee a perfect finish. However, for larger household tasks like cleaning walls and moss-encrusted roofs, a stronger jet may be necessary for which portable machines operating between 2 000 and 3 000 psi are available.

While pressure washer technology has revolutionised many domestic tasks, it is also widely used for commercial and industrial purposes, albeit most frequently as part of an automated system. For example, commercial car washes have been around for decades, as have the much larger drive-through bays used to clean buses, lorries and locomotives.