Oh, the Pressure
Saturday, June 17, 2006
Five months after carpenters screwed down the last board on my oak and mahogany deck, I rented an industrial pressure washer, cranked it wide open and learned too late why wood manufacturers warn people to think before they shoot.
I made two key mistakes. I applied a harsh wood cleaner for longer than directed. I also held the pressure wand -- rated at 3,200 pounds per square inch -- too close to the deck.
The next day, the deck's almost-new surface resembled an ancient river bed crisscrossed with furry strips of raised wood grain. A subsequent coat of cedar-toned stain made a dozen ugly gouges glare like beacons.
I cursed myself, but experts say pressure-washer mishaps are common. People ignore user manuals and damage costly decks, siding, brick or driveways. Sometimes it's worse. In 2004, an estimated 3,747 Americans needed hospital care for pressure-washer injuries, with 20 percent sustaining chemical burns to their eyes, according to the Consumer Product Safety Commission.
Manufacturers say consumers need to know the operational basics, as that can spell the difference between a job well done and a frustrating or dangerous experience.
Electric or Gas?
Both electric and gasoline-powered pressure washers excel at removing grime, oxidation and stains. Gas units are more powerful, typically generating 2,000 to 4,000 pounds of pressure per square inch (PSI) compared with 1,300 to 1,800 PSI for electric units. Both types come with adjustable nozzles or graduated tips that alter the spray pattern from pencil point to wide angle. The larger units can produce a water jet strong enough to cut through a cement block.
Electric pressure washers are fine for "light-duty" homeowner applications, said Powermate Corp. spokeswoman Nicole Toledo. Electric units are also easier to tote around and cost less than $170, or about half the price of gas units. But gas units "are the obvious choice," she said, for large projects.
In July 2005, Consumer Reports agreed, finding that gas units can clean a dirty patio three times quicker than the fastest electric units, mainly due to a larger, stronger spray pattern. Homeowners with frequent pressure-washing chores may find purchasing makes more sense than renting, the publication said. United Rentals in Gaithersburg quoted $65 for a one-day rental of a 2,700 PSI gas unit.
Easy Does It
Faced with a big project, it's tempting to rush things by pressing the water nozzle too close to surfaces. Don't. Pressure washers -- gas units especially -- can punish operator error by splintering and etching wood.
Marc Cantor, owner of Potomac Pressure Washing, has seen a multitude of do-it-yourself bloopers, including "blown-out [rail] pickets," raised wood fibers that give the deck surface a permanent furry look and "scars all over" the deck, he said. "You can definitely see the difference between somebody who doesn't know what they're doing and somebody who does."
Powermate engineer Kurt Beckman suggested testing the pressure washer on an inconspicuous spot, at low pressure. If the dirt isn't removed, move the nozzle a bit closer, but keep it within the manufacturer's specifications. Using excessive power "will rip right through your siding or wood," he said. "You could literally strip the paint right off your car." Beckman recalled that his first use of a pressure washer resulted in "holes a quarter-inch deep into my [deck's] wood before I realized it."
Powermate recommends a four-step cleaning process for decks: Remove all items from the deck and rails, apply an approved detergent, power clean the surfaces, and rinse.