Pressure Washer Buying Guide

PSI, GPM, CU—who’s making alphabet soup?

When shopping for pressure washers, the first obstacle you’ll encounter is acronyms. PSI stands for Pounds per Square Inch, and it tells you the amount of pressure that a pressure washer emits. PSI is the best gauge of how effective a pressure washer is at breaking down stains or debris.

GPM stands for Gallons Per Minute. GPM is a measure of the quantity of water that the pressure washer sprays and tells you how quickly the pressure washer removes loosened debris—higher GPMs result in the ability to clean larger surface areas in less time.

Some manufacturers combine these ratings to determine the Cleaning Unit, or CU, which is sometimes written as UCE. Manufacturers determine the CU by multiplying the PSI by the GPM; the resulting figure represents the amount of cleaning capability promised by the pressure washer.

Too much pressure?

Higher PSI does not necessarily equal better cleaning, as some homeowners who’ve learned the hard way can tell you. If the pressure washer’s PSI is too powerful for the surface being cleaned, it may actually damage the surface itself, resulting in scratches or surface deterioration.

As a general rule of thumb, electric pressure washers are less powerful than gas pressure washers, making them the better choice for residential users. Electric pressure washers can also be used safely indoors. Commercial or industrial applications call for more powerful gas pressure washers, but emission-emitting washers should only be used outdoors or in large, well-ventilated areas.

Look for 1,200 to 1,350 PSI for car or patio-furniture washing and 1,500 to 2,200 PSI for decks. Cement patios require a bit more power; pressure washers with 2,200 to 3,000 PSI will get the job done and will also be suitable for washing the siding on your house. If you need to clean concrete or strip paint, you’ll need the full power of a 3,000 to 4,000 PSI pressure washer behind you.

Keep in mind that these PSI recommendations are only guidelines. You should always carefully inspect any surface you’ll be cleaning with a pressure washer. Softer surfaces, like wood, respond best to low PSI and wide-spray nozzles that disperse pressure over a larger surface area. Zero degree nozzles, which deliver pressure into a small, concentrated spray, are best for tough jobs on hard surfaces like concrete but will damage anything softer.

Motors

The pressure washer’s motor and pump are what creates the washer’s pressure. Without them, all you have is an odd-looking hose. Pressure washer motors come in two types: electric and gas. Electric motors are less powerful, but their lack of emissions makes them greener overall and safe for indoor and outdoor applications. Gas pressure water motors are more powerful and best used for commercial or industrial cleaning that’s outdoors or in very well-ventilated areas.

Electric pressure washer motors are either universal (brush) motors or induction motors. Universal motors are inexpensive, but their less-efficient construction makes them a poor choice for long-term use. Induction motors are more expensive, but they last significantly longer and are a good choice for a long-term investment.

Gas pressure washer motors are measured in Horsepower (HP). Don’t think that a lot of HP means a better pressure washer. It’s the type of pump, not the number of horses, that determines performance.

Pump it up

The pump is the key component that determines the power of a pressure washer. Ceramic pumps, also called triplex plunger pumps, are the best long-term investment. They last longer than axial pumps, and mineral deposits found in hard water won’t clog them. Ceramic triplex plunger pumps are also less expensive to repair than axial pumps.

Brass and stainless steel axial pumps are also good choices that will last for many years. It’s best to avoid aluminum pumps, because this material will corrode and clog from the minerals in your water. If you live in an area with hard water, choose a pressure washer with a brass or ceramic pump for performance over the long term.

Pressure washer pumps connect to motors in two ways: direct drive and belt drive. Direct-drive pumps are attached to the motor, have a longer life and operate more efficiently than belt-driven pumps. Belt-driven pressure washers have a belt running between the motor and the pump. The belt is subject to wear and will fail at some point during the life of the pressure washer.

Accessorize

Accessories can change a pressure washer from an occasionally used amenity to a feature of daily life. Most pressure washers come with a range of nozzle options, from fan spray that spreads the water over a 45-degree angle to a 0-degree nozzle that concentrates all of the pressure washer’s force into one point.

Some pressure washers include an optional second tank that you can use for spraying detergent or cleaning chemicals along with water. When using detergent or cleaning chemicals, be sure to check the manufacturer’s specifications to determine what’s safe to use so you won’t damage the equipment or the surface you’re cleaning.

If you’re battling mud or caked-on dirt, look for a pressure washer with a brush attachment that can scrub off debris. A spray arm extension is also a must for concentrating the spray in high or hard-to-reach areas.

Need to know more?

• How to Use a Pressure Washer
  http://www.ultimatewasher.com/how-to-washing.htm
• Pressure Washer Maintenance
  http://www.outdoorcleaning.com/maintenance/maintain/index.cfm
• How to Pressure Wash Your Deck
  http://www.pressurewashersdirect.com/catalog/howtocleandeck.php