Vehicle Washing

A guide to pressure washers and vehicle washing systems

According to Dunn, many pressure washer companies advertise their units’ performance based on the maximum performance of the high-pressure pump coupled to the engine or motor. “While this may be the easy thing to do it is more often than not the wrong thing to do.”

For example, some companies advertise that their units will produce 4 gpm at 4,000 psi with a small compact frame and direct-drive pump and a 12-horsepower gas engine. But how can a consumer know if the unit will actually provide the advertised performance?

There are a couple of easy equations that can be used to see if the manufacturer is being honest about the unit’s performance, he says.

For a gas and diesel engine units:

(gpm x psi x 1.3) divided by 1,460

For electric motor units:

(gpm x psi) divided by 1,460

If the unit has a generator, add 1.5 to 2 to the result. If the unit has an axial pump, deduct 0.5 from the result.

In the example: 4.0 gpm times 4,000 psi equals 16,000 divided by 1,460 and then multiply by 1.3 equals 14.2. This is the net horsepower required by a gas or diesel engine to power a crankcase pump and achieve the advertised performance.

“The net horsepower of the engine in question is 12 so the unit can either produce the advertised gpm or the advertised pressure, but not both at the same time,” says Dunn. “Engine net horsepowers are available from the local pressure washer dealer or from the engine manufacturer.”

5. Are the accessories durable and comfortable to use?

Sometimes the purchaser of the pressure washer puts all of their focus on the unit without any consideration for the accessories that also come with the unit, says Dunn. Simple things like an ergonomically designed trigger gun, kink-free hoses and easy-to-change high pressure nozzles can make the difference between a terrible cleaning experience and an enjoyable one.

“A lot of thought should be given to the operator when making a purchase decision,” he recommends. “Using uncomfortable or unwieldy accessories can fatigue the operator or even lead to workplace injury.”

6. Is it safety and quality certified?

UL-1776 is a regulation that describes in detail a variety of features that pressure washers should have to avoid injury. These include: safety relief valve, hose guard for burst protection, warning labels, ground fault circuit interrupter, high pressure release value and specified lengths for the wand and electrical cord.

“Make sure the certifying agency is a Nationally Recognized Testing Laboratory (NRTL),” stresses Dunn. Performance certification is also very important.

“The Cleaning Equipment Trade Association (CETA) gives manufacturers a stiff set of guidelines to build equipment to. CETA requires that the actual performance of the machine not vary by more than 5 percent of its actual performance. Typical consumer-duty units are not performance certified and the performance can vary by up to 20 percent.”

7. Is it backed by a solid warranty?

Quality pressure washers will have a minimum of a 5-year warranty on the pump and frame and a 3-year warranty on the gasoline engine, he says.

Another important question to ask is: How many trained, warranty service centers are there and is one close by.

“Despite their simplistic design, be assured that not all pressure washers are created equal,” he concludes. “Nonetheless, you can have confidence in making the right choice when you ask the right questions.”


For some maintenance and fleet operations, it might make sense to install a vehicle washing system, says Marc Tyndale, a partner of Car Wash Systems. Based in, Harrisburg, PA, Car Wash Systems provides consulting, design support, fulfills equipment needs and offers service and supplies associated with automated or manual vehicle wash equipment.

When considering a vehicle washing system, Tyndale says an operation should ask itself the following questions when deciding at what point automated washing versus manual washing makes sense, and what type of wash facility would best suit its needs.

1. How many passenger vehicles (cars, pickups and passenger vans) will be washed in a day, week or year?

“It is essential to know how many vehicles get washed daily for many reasons,” he stresses. “Fleets shrink and grow so it is imperative to plan for the future.”

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