High-Pressure Water Jetting for Cleaning Walls

Parts of a Pressure Washer

• A high-pressure water jetting washer has three main components: the pump, the unloader and the spray gun. The pump runs on either gas or electricity and is connected to a water intake; water is supplied via a hose connected to the intake. The pump builds up the pressure to up to around 1,000 PSI for a small home unit, and up to 20,000 PSI for industrial-strength washers, which controls the amount of water that is released through the spray gun when the trigger is pressed.

Gas vs. Electric Pressure Washers

• In general, professional grade pressure washers are machines about the size of a large lawn mower or larger that run on gas. Gas pressure washers have the highest PSI and are best for large jobs. Electric pressure washers tend to be smaller, about the size of a vacuum cleaner or smaller, with lower PSI, making them a better option for smaller household jobs and for when you need a more portable washer. With electric washers, you need an extension cord, which can be cumbersome; gas pressure washers are cordless, though they're still connected to a water hose.

Safety Precautions

• Even if you're pressure cleaning without chemicals, it's important to wear the proper protective gear when using a pressure washer. Eye protection is necessary, because the high pressure water jets blasts away debris that may become airborne. Ear protection should be worn if the pressure washer you're using has a loud pump. If you're using chemicals in the pressure washer, your face and clothing should be covered, or you should wear work clothes. Never spray pressurized water at people, pets or fragile items.

Using a Pressure Washer

• Once the pressure washer unit is connected to the water hose and turned on, test an inconspicuous area of the wall to make sure the water jets achieve the desired result. For cleaning, keep the PSI around 1,000 to 2,000. For stripping and blasting, a high PSI combined with a narrow opening in the top of the nozzle increases the intensity of the jet. Point the nozzle at a 45-degree angle toward the lowest part of the wall and squeeze the trigger. Move the water jet back and forth and move slowly upward. Don't allow the jet to concentrate on one spot for too long, as it may cause damage.