Correcting Common Pressure Washing Misconceptions

By Diane M. Calabrese / Published July 2021

Sometimes we are just wrong. We may misunderstand, or we may stop short of taking in all the information available. Whichever the case, the word “misconception” rings softer than the alternative. And getting it right—correction—is what matters.

     Misconceptions about pressure washing can occur at any point along the manufacturer-distributor-contractor-customer chain. But let’s put focus on the vital link in the chain, the end user.

     Contractors must know their machines and their substrate. Making a good match requires a methodical approach. A “good enough” approach is a misconception.

     “I think the biggest mistake is not recognizing the power of the pressure washer,” says Bryson Sharp, design engineering manager, Northern Tool + Equipment in Faribault, MN. But other issues may also stem from misunderstanding.

     “It could be choosing the incorrect nozzle for the job (zero degree versus a 25 degree), positioning the nozzle too close to the item being cleaned, or having the unloader pressure set too high,” says Sharp.

     How would Sharp make a correction? “The best advice is to sneak up on the item that you are cleaning, stand back, and move closer to achieve the proper level of cleaning,” he says. “Start with the unloader pressure set lower to start and increase it gradually. Choose the spray nozzle with the least amount of impact and increase as needed.”

     The better a contractor understands the machine being used, the more exacting the outcome of any job. Sharp gives another example of a misunderstanding.

     “Another common misconception is that the pressure washer operator must pull the trigger regularly to prevent pump damage from overheating the water while in bypass,” says Sharp. “While this is true, many pressure washers today have a feature called a ‘thermal relief valve,’ or TRV. If your pressure washer has a TRV, it will protect the pump by allowing the heated water to escape before the elevated temperatures can damage the pump.”

     Manufacturers want end users to deploy equipment for its intended purpose. The more carefully a contractor selects a machine, the better the results at a customer’s residential or commercial site will be.

     Tutorials and guides at manufacturers’ websites aim to prevent end users from having misconceptions about their equipment. Sharp’s company, for example, offers a “How to Choose the Right Pressure Washer” guide, which is pithy and potent. Along with power and speed, temperature (cold or hot water), and location (indoor or outdoor cleaning), prospective buyers are advised to gauge their frequency of use.

     Manufacturers also offer training for their distributors and work with them through professional organizations such as the Cleaning Equipment Trade Association (CETA) to ensure frequent communication and foster understanding. The more accurately information is passed along from manufacturer to distributor to con-tractor, the more unlikely that a misconception will occur.

Flow Over Pressure

     As misconceptions go, Karl Pasternak, the technical manager at Dynablast Equipment—a division of John Brooks Company Limited in Mississauga, Ontario, Canada, singles out pressure for attention.

     It is a misconception that “pressure is the most important performance criteria—pressure is king—when buying a pressure washer,” says Pasternak. “This is simply not the case.”

     To highlight conventional thinking on pressure, Pasternak uses his coinage “flow cleans, but pressure sells” around the office. “It’s important to have a good blend of flow rate and pressure to have any effective cleaning.”

     What about the pressure? “The main reason to use a pressure washer to begin with is to save time,” says Pasternak. “When you have a high output pressure, say 1900 psi with a water flow rate of 1.4 gpm, which I’ve seen advertised, what you end up with at the outlet of the nozzle is mist. Not the most effective cleaning combination.”

     Indeed, Pasternak says he enjoys reading the weekly newspaper to evaluate how pressure washers are marketed. “I chuckle to myself about how creative the marketing people that work for the automotive supply and hardware stores chains have become.” Among the specifications and claims made, however, flow rate is often absent.

     “They make claims like ‘powerful enough to tackle any job around the house,’” says Pasternak. “Imagine trying to wash an ATV with two inches of dried mud with a pressure washer that produces 1900 psi mist? I see outlandish performances like 2050 psi with a flow rate of 1.5 gpm all on a standard 120-volt 15-amp plug. I can’t help but wonder, how does that work? How is it possible to even get this performance? Is the idea to save on water? This may not be true. Instead, you will just be washing for longer, perhaps even consuming more water.”

     Pasternak again emphasizes it’s a misconception to consider flow and pressure independently. “A combination of flow rate and pressure is the key to any effective cleaning,” he says. “Anything over two gpm starts to become more effective. Also, there need not be such high pressures when the flow rate is less than two gpm. As you increase the flow rate from two, three, four to even five gpm, the cleaning becomes way more effective even at low to moderate pressures.”

     And Pasternak reminds us there is a place to begin when thinking about interplay between pressure and flow. “A good combination is four gpm with an operating pressure of 2500–3000 for general cleaning,” he explains.

     A subordinate misconception is the nature of the water supplied to the machine. “If the aim is to provide a mobile wash service, there is a fine line as to how much water flow will make it to the pressure washer pump,” says Pasternak. “If you travel from site to site relying on your customer’s water supply to provide water to your machine, you really have no idea what flow rate you have getting to the inlet of your pump. They could be on town water or on a well; the water supply can vary dramatically.”

     Recognizing the variability, what can the contractor do to counter it? “A rule of thumb I like to use is [to obtain] twice the advertised flow rate of your washer available at the inlet of the pump,” says Pasternak. “This will almost certainly prevent dreaded cavitation wearing out the inside of your pump. I realize this may be far from what reality allows, but the closer you get to this number the better.”

     When contractors understand how to get the optimal performance from their machines, the entire industry gets a boost. And Pasternak is happy to make recommendations to help owners get that performance.

     “Another tip I tell people is, don’t adjust the pressure by backing off the unloader valve—the pressure control regulator,” says Pasternak. “I suggest they use larger-sized nozzles to get the lower pressures—this will maintain the maximum output flow rate. If you simply reduce the pressure by backing off the unloader valve, you will just bypass water flow internally, and what you get at the outlet of the nozzle is less flow.”

     Pasternak sums it up this way: “Flow rate is as important as pressure. Pressure may help to penetrate the soil you are cleaning, but it’s the flow rate that washes it away.”

Those Who Do

     More and more contractors are also teaching these days. Not only do they share expertise with those new to the industry, but they educate customers. With website FAQs or bullet points on misconceptions or myths about the process and logistics of pressure washing, they do more than allay concerns of prospective clients. They also demonstrate their expertise.

     Professional contractors want their customers to be informed. One of the first misconceptions most address is that a homeowner can take on exterior cleaning as a do-it-yourself project and get good results.

     The misconception is equating good results only with a clean surface. If damage is done to the house because too much pressure was used or an angle was bad, allowing seepage, that’s not such a positive outcome. Similarly, if damage is done to anything in the environs—plants, cars—or the DIYer is injured, that’s definitely a bad outcome.

     In 2021, few contractors harbor misconceptions about licensing or wastewater disposal. They know that licensing, discharge permitting, and rules for wastewater collection differ with locality, and if they work in more than one jurisdiction, they may be subject to different regulations in each.

     Distributors, like manufacturers and contractors, do their part to promote understanding and prevent misconceptions. Strong distributors offer extensive introductions to their products online and in their shops. Their efforts to educate alleviate misconceptions.

     For example, is it just a water reclamation system the contractor requires? Or is it a recycling system? Moreover, which sort of waste stream must be recycled—particles or oil?

     A berm to contain wastewater often took care of things in the past. It is a serious misconception for contractors to not expect much more precise containment—and collection—will be required in the future.

     Willingness to learn and change equipment and techniques for best practice are the surest ways to avoid misconceptions (aka being wrong).