Pressure washing, also called power washing, is the first step in preparing your homes exterior for painting. All exterior paints and coatings must have a clean surface to adhere to in order to last.

Applying any primer or paint over dirt will lead to premature failure of the paint job. The most popular way to achieve clean siding and trim ready for paint is using a pressure washer.

This is a powerful machine that uses pressurized water to remove dust, chalk, pollution, mildew and even some loose paint. These machines can be either electric or gas powered, with gas powered models being the most powerful.

The procedures for washing a home prior to painting is easy to understand, but these machines are powerful and if misused can do considerable damage.

Getting to Know Your Pressure Washer

The most obvious place to start is with the owner’s manual, but if you rent a machine the manual doesn’t come with it. As a tool renter you are expected to know how to use the machine. Ask someone to demonstrate how the equipment works and answers all your questions before you leave the rental store.

Fortunately, every pressure washer comes with some basic parts and has similar requirements.

The basic parts are the pressure hose, the spray wand and gun, the spray nozzles and the water pressure control knob. The pressure hose and gun is simple to understand. The real finesse is gaining an understanding of the use of pressurized water and the spray nozzles.

Another aspect of a pressure washer is the supply hose, garden hose. Most garden hoses are 1/2 inch in diameter and could restrict the water going to the washer enough that some problems could occur. Restricting the water flow can cause damage to the pump. I recommend a large, 5/8 inch, commercial hose instead.

Safety Issues

Using a power washer can be dangerous. Never point the nozzle at a person or yourself. Imagine what kind of damage 1500-3000 psi water could do. Close proximity to these pressures will tear into the skin and cause serous injury.

Another aspect of the pressure is the recoil from the gun and wand when the trigger is pulled. This will be difficult to deal with, especially on a ladder. Plus, you will need to use all of your balance and a few muscles you didn’t know you have. Pressure washing will take a surprising amount strength and energy. Know your limitations.

Be careful of electrical power sources; such as lights, outlets and the meter box. Electricity and water is a bad combination. Angle the nozzle away from these areas and don’t blast them directly.

Water Pressure — How Much Is Enough

You will have a broad range of pressure and power to use with commercial (professional) machines, but most of the time you won’t need the highest setting. All too often people, homeowners and pros alike, will turn up the pressure thinking that more must be better. This isn’t always the case.

• For basic cleaning, 1500-1800 psi is good. This is more than enough to remove dust, dirt, spider webs and pollution. This is also a good pressure for removing mold when a cleaner is used.
• For an intense cleaning with the intent to remove some loose paint use 1800-2500 psi. This will be enough pressure to remove loose paint from most surfaces.

Maximum pressure for most machines is 3000 psi. At this pressure many surfaces can be damaged. Be careful, wood siding can be damaged with pressures as low as 1500 psi. This high pressure can be useful for carefully stripping sound masonry surfaces.

Choose the Right Pressure Washing Nozzle

Choosing the right nozzle, or tip, is important. The spray nozzle will affect how the pressure is applied to the surface. You want a wide fan that is suitable for the surface you are cleaning.

Professional pressure washing machines use color coded nozzles with quick disconnect connectors. The colors indicate the width of the fan (degree) and the amount of potential washing ability. The most useful nozzles are yellow, green and black.

Red (0° degree) – This nozzle produces a straight stream of water. Normally not used for washing houses as it can damage all surfaces and cause the need for additional repair. It can be useful for rinsing high areas from the ground, such as soffits and fascia boards. Be careful when using this nozzle.

Yellow (15° degree) – This pressure washer nozzle has a tight sharp fan that is useful for removing paint. When held at a 45 degree angle you can use it like a paint scraper. It is also used where extra power is needed.

Green (25° degree) – This is the primary washing nozzle. It is used for general cleaning when maximum power isn’t needed. Think of this as a medium power nozzle. Also used for sweeping leaves, debris and caked dirt from driveways and sidewalks.

White (40° degree) – This nozzle has a wider dispersion of the pressurized water keeping it limited to rinsing and gentle washing. Can be used for washing and rinsing glass or washing vehicles.

Black (Chemical) – Used for chemical application and used with downstream chemical injectors, if your pressure washer is equipped with this feature. This isn’t a high pressure nozzle and, by itself, will not actually do any cleaning. They are used to apply the chemical and water mixture in a wide low pressure spray. When using this nozzle a siphoning action is created which allows the chemical injector to siphon the chemical and mix it with the water flow.

Turbo Nozzles – The turbo nozzle uses a zero degree stream of water and spins it in a circle. They will produce both high impact and good cleaning coverage. This is a very powerful accessory that is very useful in the right situation, but they can also cause a lot damage to soft materials like wood siding. A turbo nozzle is a perfect solution for producing a powerful and thorough cleaning of concrete.

The most useful pressure washer nozzles are the yellow (15° degree) and green (25° degree) and will be the ones used most often during pressure washing as a part of the exterior preparation before painting.

Suggestions before Starting to Pressure Wash

• Make sure all windows and doors are fully shut and secure.
• Do any windows or doors leak during a rainstorm? If so, be careful while trying to wash around these areas.
• Clear away all items from around your house, especially outdoor furniture that could be damaged from the dirt coming off your house. Also, move any items that you could trip over.
• Having a second person around will be helpful. They could help with the hose, keeping it from messing up flower beds, etc.
• Turn off the power to light fixtures and electrical outlets at your home’s main service panel.
• If it’s windy, don’t wash or be very careful when on a ladder. You will already be fighting the water pressure; there is no good reason to fight the wind as well.
• You will become tired and fatigued from fighting the water pressure. When you do, take a break.

Basic Pressure Washing Recommendations

Pressure washing a house requires some simple ideas and considerable effort on your part. It is best to make it easy on yourself and start with a lower pressure setting and a larger nozzle.

• Adjust the pressure for maximum cleaning without causing damage. Start with 1500 psi and increase if necessary, 2000 psi is plenty for most materials. Start with a 25° degree nozzle. A 15° degree nozzle has a more powerful spray and can do damage if improperly used. You can change the nozzles if it seems to be taking to long to achieve your results.
• Start pressure washing at the top and work your way down. This will wash the contamination down the walls and not onto previously cleaned areas.
• Hold the nozzle 12 inches from the siding. Any closer could do damage. If you want the spray closer to the surface, turn down the pressure and readjust when you are comfortable working at a closer distance.
• Spray in a downward angle. Never spray up and under lap siding. The water will enter the wall and could cause peeling of the paint at a later date. Plus, angle the spray away from windows and doors.

Pressure Washing With Soap and Other Cleaning Solutions

Cleaning solutions can be used with most types of washers, but the use of soap isn’t mandatory. Most of the time plain cold water will do the job just fine. If soap or other chemicals are used, don’t allow them to dry on the surface.

• Soaps and cleaning solutions should be environmentally friendly and have a neutral PH. A mild soap solution will not harm the landscaping or the painted surface.
• Start applying the soap solution from the bottom to the top. This will allow the solution to loosen dirt and grime before the final rinse. Allow the soap to sit on the surface for 10 minutes before rinsing.
• Adjust the pressure to 1500 psi when rinsing with a soap solution. This procedure does not require the use of high pressure. You can also use the white (40° degree) nozzle for rinsing, since it has a wide dispersion. Adjust the pressure accordingly for the larger nozzle.

Start-up Procedures

• Gas Powered – Check engine oil and add if necessary.
• Check pump lubricant and add if needed. Typically 30 weight non-detergent oil, follow manufactures recommendations.
• Inspect and connect hoses and gun. Make sure all connections are secure before proceeding.
• Choose and install the nozzle. The nozzle must be fully secure, double check. If it’s not, it could become a projectile when the trigger is pulled.
• Connect garden hose. (Recommend larger commercial hose.)
• Turn water on fully. Try to not use the cloths washer and dishwasher while using a pressure washer. It needs all the volume it can get.
• Pull the trigger and purge all the air from the pump and hoses. Don’t start the machine until a steady stream of water appears.
• To start, pull the trigger fully open on the gun. If you don’t do this, possible damage can occur to the pump. Also with a gas machine you could hurt yourself when pull starting the engine.

These are some basic procedures for pressure washing painted siding. Stained wood siding such as cedar lap and T1-11 will require slightly different procedures in order to wash the exterior for re-staining. Pressure washing a home with stain, instead of paint, is the most crucial step when restaining a home.