Pressure Washers: What To Look For

Pressure washer basics

Pressure washers (also called power washers) are basically a pump (to pressurize water) that's powered by an electric motor or gasoline engine. The water flows through a wand with a nozzle at the end that controls how much the water spreads. A trigger turns the flow on and off. Pressure washers are rated by three specifications:

• Pounds per square inch (psi): the measure of the dirt-loosening pressure (important for stain removal).

• Gallons per minute (gpm): the measure of the water flow that washes the loosened dirt away (important for speed).

• Cleaning units (cu): an overall estimate of cleaning power, calculated by multiplying psi by gpm.

Even if your pressure washer has a very high psi rating, the job will take a long time if it has a low flow rate. For some jobs, too much pressure is a disadvantage, as it can damage car finishes and roughen wood. For the most flexibility, look for a pressure washer with adjustable pressure settings and interchangeable nozzles.

Experts suggest erring on the side of buying a bit more power than you need, since running a pressure washer at full blast can wear it out too quickly. By comparison, a garden hose delivers about 40 psi.

• 1,000 to 1,500 psi: good choice for washing cars, bicycles, lawn furniture and grills

• 1,400 to 1,850 psi: appropriate for cleaning a patio or small deck

• 2,000 to 3,000 psi: more power for cleaning a large deck or washing siding

• 2,800 to 4,000 psi: best for cleaning stained concrete, stripping paint

Experts estimate that a pressure washer with 2,000 psi and 2 gpm can clean about 5 to 7 square feet per minute, while boosting the flow rate to 3 gpm lets it clean about 8 to 10 square feet a minute. We found quite a few reviews from owners happy that they moved up to a more powerful pressure washer with a higher gpm, saying they've cut cleaning time in half.

Consumer-grade pressure washers use only cold water. Water that's above a certain temperature (usually around 104 degrees Fahrenheit) can damage the unit. However, experts say that it takes hot water (plus detergent) to blast away grease and oil, so for this kind of job, you'll probably need to rent a hot-water pressure washer. This report covers only cold-water pressure washers appropriate for residential use.

Gas vs. electric pressure washers

Gasoline-powered pressure washers provide the most power -- important if you want to strip paint from siding, clean second-story siding or have huge expanses of deck and driveway to keep clean. However, the extra power comes with significant trade-offs. Gas pressure washers are louder, harder to start and more expensive to fuel. They're also worse for the environment because of engine emissions, gasoline fumes and the possibility of spilling gasoline while refueling.

For these reasons, most experts recommend electric pressure washers if they'll do the jobs you handle most often. Their lower power is much safer for car and bicycle paint, and less apt to raise splinters on a wooden deck. Electric pressure washers are also quieter and easier to use -- just flick a switch to start the motor. They not only pollute less but also cost much less to operate -- especially at current gasoline prices. In the October 2007 issue of Workbench magazine, Bill Link reports that he used one gallon of gas to clean just a 12-foot-square deck. Gas pressure washers also require oil and maintenance parts such as spark plugs.

Electric pressure washers are ideal for small jobs, as well as being lighter and easier to move around than gas models. Plus, you can safely use them indoors. Last but not least, they cost less. You can get an electric pressure washer capable of efficiently cleaning a patio or small deck for around $200.

They do, however, have their own set of drawbacks. They can only be used within about 100 feet of an outlet, and some require a 20-amp circuit. You need a ground fault interrupter on the circuit for safety -- often built into the cord. The lower price also means less durability; experts call cheap pressure washers that use axial pumps "throwaways."

It's easier to find gas pressure washers that are built for durable, multi-year use, with top-quality pumps that can be repaired, but many of these are priced beyond the average homeowner's budget. Unless you know you'll use it often, experts say it's better to buy an electric pressure washer for routine use and rent a gas pressure washer for occasional big jobs like washing siding.

Pressure washer buying considerations:

Reviews recommend considering the following factors when choosing a pressure washer:

• Pressure washer power is expressed as cleaning units (cu), calculated by multiplying the pressure per square inch (psi) by the water flow rate in gallons per minute (gpm). More power usually adds cost and weight, so there's no point in buying more than you need. On the other hand, if you try to use a smaller pressure washer for a task that calls for more power, it will take a long time and may wear out the pressure washer altogether.

• Ceramic triplex plunger pumps are better than axial pumps. They last longer and are also economical to repair. Axial pumps are usually just replaced when they wear out or break. Ceramic or ceramic-coated plungers are also superior to aluminum plungers, especially if you have hard water (mineral buildup on aluminum can be a problem). A brass manifold is better than aluminum, and stainless-steel moving parts are also a plus.

• Consider renting. Experts say that most homeowners only use a pressure washer about 20 hours a year, often even less. If you do plan to use a pressure washer for an occasional big job, such as cleaning siding or a big deck, consider renting one instead.

• Threaded brass connections with O-rings are better than bayonet connections. We found quite a few complaints about connections leaking, so this can make a difference in your satisfaction.

• Pneumatic tires absorb some of the vibration. They can reduce noise, ease mobility and keep the pressure washer from dancing around during use. Reviews also like "never-flat" tires, however, so it's a trade-off that boils down to personal preference.

• Not all pressure washers let you adjust the pressure. This may seem surprising, but it's an extra feature found mostly on more expensive professional-grade models.

• Separate spray tips give you more options. It sounds convenient to have one adjustable tip, but some owners say they wish they had more choice.

• Electric induction motors are better than universal motors. They're quieter, more durable and run cooler, so the pump lasts about three times longer.

• Turbo nozzles do add stain-removal power, but can leave streaks. Experts don't recommend using a turbo nozzle to wash cars, noting that too much pressure can also damage the paint. Turbo nozzles do speed cleaning for decks or grills, and experts say a turbo nozzle can clean concrete about three times faster than a regular nozzle.

• Some electric models require a 20-amp circuit. Keep in mind that pressure washers that need a higher-amperage outlet also need a special extension cord, which can be quite expensive.

• On most electric models, releasing the trigger cuts the motor, saving electricity and eliminating unnecessary noise, but also protecting the power washer from damage. Some manufacturers call this a "total stop trigger gun." On some electric and most gasoline models, however, you'll need to manually turn off the engine if you take a break longer than a specified number of minutes. This "break time" varies from less than two minutes to five minutes. The longer time is clearly more convenient.

• Check return policies as well as service and parts availability before buying. Gasoline pressure washers are especially hard to ship for service, so it's better to buy a brand that can be repaired locally. Consider the cost of accessories if you want them.

The average municipal water system provides about five gallons per minute of water, so getting enough water flow won't be a problem. If your household water draws from a well, you'll need to be sure you select a pressure washer with an appropriate gpm rate for your well. (You can check your water system's gpm rate by running water for one minute into a 5-gallon bucket.)

For gas pressure washers, find out how long you can take a break from spraying. When you release the trigger, pressure and heat build up that can start damaging the pump within minutes. Sometimes the time limit is hidden deep in the instruction manual. "Unloaders" are designed to minimize pressure buildup, while "bypass valves" or "thermal relief valves" are designed to cool the water (which the engine keeps heating up). Experts say some of these devices work better than others, but it's still safest to be sure to pull the trigger briefly at least once a minute to send some cool water through the pump.

Note that pressure-washer warranties don't cover anything the manufacturer considers to be the owner's fault. Gas pressure washers require a lot of maintenance -- oil changes, spark-plug replacement and fuel-saver additive to keep water out of the gasoline. Pumps need to be winterized with great care, or the pressure washer won't start the following spring. Our Useful Links page has more information on maintenance.