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What should you not pressure wash? What the professionals say

Pressure washers are powerful machines that are helping to clean the exterior of your house efficiently. They use high-pressure water to blast dirt away. But in some circumstances, this does more harm than good. Using high pressure on concrete driveways, bricks, and other hard surfaces will be fine. For some softer surfaces, you have to use lower pressure. But there are also some materials where you should not use high-pressure water. Materials that can be damaged should be handled carefully and better cleaned differently.

What should you not pressure wash:

In general, you should not pressure wash materials that are painted. Also, asphalt roofing, Electrical boxes, outdoor lighting, your AC outdoor unit, old motar, grout and windows. Also, take care of the pressure when cleaning your car and engine, bikes, old plastic, and other soft material.

By the end of this article, you will learn specific precautions to follow while using a pressure washer. We will also provide you with the reasoning about why you should not use pressure washers inside your home and which surfaces you should never pressure wash.

What should you not pressure wash, 21 examples

The following table shows 21 examples of materials that you should not pressure wash:

Why should you not pressure wash it?
All painted material
The high water pressure will remove, or weaker the paint on most materials
Stained wood
You will remove the stain from the wood
Lead Paint
The lead paint will get into the air
Asphalt roofing
You will remove the granules from the asphalt roof or damage the shingles
Old wood
Old wood can be weaker
Old plastic
Be careful with old plastic. Some can be weakened by the UV rays from the sun and can be damaged easily
Electrical boxes, equipment, and Panels
The water can force itself in the box or panel and create a short circuit
Outdoor lighting
The water can find its way to the internals of the light
Air Conditioner
The pressure can damage the internals of the outer unit
Old Mortar
Old mortar can be weakened over time and can easily damage
Grout between tiles
The pressure can wash away the grout. Most grout is also not waterproof
People and Animals
It does not need an explanation
Plants and trees
You will wash away most plants and damage trees
The pressure can crack the window
High-pressure water can damage the paint
Water can find its way in specific components like for example, the fuse box
The water can enter some more delicate areas like the crankcase or wheel bearings
The high pressure from a different angle can damage the gutter
Vinyl Siding
The siding can be damaged easily
Most garden tiles
Be careful not to remove all the sand between the garden tiles

What should you not do with a pressure washer?

While pressure washing any surface, ensure that you are not using it at a higher pressure than what is recommended. You should use detergents along with pressure washers to get rid of older and tougher stains. Use the correct nozzle for the job. Different nozzle types have different spraying patterns. And different surface types require different spraying patterns to avoid damage. It would be best if you do not use your pressure washer on air conditioners, old mortar, and plants.

Do not use high-pressure water for some materials

The pressure washer uses high-pressure water to clean different surfaces easily. This pressure is significantly higher than normal water from the tap. You must adjust the pressure of water according to the strength of the surface you are cleaning. If not, you could end up damaging surfaces like vinyl sidings, wood, or your car.

Do not use water only

Pressure washers are well suited to clean surfaces with tough stains that cannot be removed using a normal hose. To clean some stains, it helps to use a detergent before pressure washing it. This will break up the dirt and kill mold. After applying the detergent on the surface, wait for at least 5 to 10 minutes and then clean it using your pressure washer.

Do not use the same nozzle for every surface

Every surface requires a different spray pattern of water for effective cleaning. There are a variety of nozzles that can be used at the tip of the pressure washer. They can produce spray patterns ranging from wide to narrow streams. The basic rule is that: the more narrow the nozzle, the higher pressure of water. To wash surfaces like sidings, use a wide 40-degree nozzle. A narrow 25-degree or even 0-degree nozzle works best to clean the dirt from concrete surfaces and remove older and tougher stains.

Do not use the same spray’s angle for every surface

For an effective cleaning with the pressure washer, you must adjust the angle of the water spray according to the surface you are washing. Use 90 degrees for tough stains. But cleaning the underside of the patio table or siding is better using a lower angle.

Do not pressure wash every surface

Although the water pressure can be changed for most pressure washers, some areas and surfaces should not be washed. Even with the lowest PSI setting. Some areas in the house already show the sign of wear and tear, and pressure washing these surfaces can easily cause damage.

Do not use hot water for some materials

Power washers are pressure washers that use hot water. The hot water helps to clean the surface faster. But be careful with some materials, as hot water can easily damage them.

Do not pressure wash air conditioners

At the start of every summer season, most people think it is good to clean their air conditioner. But do not use a pressure washer for this. The water can damage the fins of the machine. It is better to use a vacuum and hose to clean the outside and inside your air conditioner outdoor unit.

Do not pressure wash plants

The pressure from a pressure washer is much higher than that from a hose. Never use it to water or clean your plants as it will most certainly destroy them.

Why should you not pressure wash your house?

The high-pressure water can seep through small cracks in the wall to the inside of the wall. This can result in unwanted moisture and humidity. Also, using the pressure washer at high PSI settings can result in cracks and holes in the wood. And it can damage old mortar or loose paint on the surface.

Many people pressure wash their house, but only a few people know what damage it can do. To paint your house, cleaning the paint is the first step. But if you want to use your pressure washer for this, it should be done correctly. With the correct pressure, nozzle, and angle. If not, it can cause damage to the inside of your house’s walls and other areas.

Reason 1 not to use a pressure washer to clean your house: Water inside the walls

The pressure washer shoots water out of its nozzle at high pressure that can reach 3000 psi. This high pressure can be destructive. It can blast through solid wood and some other materials if you do not use the correct pressure. Also, use the correct nozzle, and maintain a proper distance between the nozzle of the pressure washer and the surface.

If you have areas in your house with wood sidings and shingles, there is a high chance that pressure washing will blast the water inside the wall cavities and plaster. These surfaces always are full of joints and cracks. The pressure helps the water find a way through these. And once inside, it is challenging for it to evaporate.

Reason 2 not to use a pressure washer to clean your house: Loose mortar

If you have a brick house, or part of it uses bricks, you must be thinking that it is ok to use a pressure washer to clean it. Generally, using a pressure washer to clean bricks is fine. But, if there is any loose mortar on the surface, you will easily wash it away. Or you will weaken it and end up damaging it instead of cleaning it. Start cleaning with low pressure, and only increase it when needed.

Reason 3 not to use a pressure washer to clean your house: Wood damage

Some painters use a pressure washer to clean wood and remove the paint. They use a high pressure only on the hardwood. Softer wood can easily damage. Using high pressure can lead to holes and cracks in the wood.

From the above discussion, we can say that you have to take care when using a pressure washer to clean your house. For some surfaces, it is ok. For others, it is not. It is important to check before starting to keep the surface you want to clean free from any damage.

Can you power wash inside your house?

In general, I do not recommend using a pressure washer inside your house. Although you can adjust the pressure of your pressure washer, it is still high enough to damage most items and materials. Part of the spray will bounce back and add a lot of extra moisture. Glass inside your house can easily crack. In some circumstances, you can use the pressure washer to clean the bathroom floors, bathtubs, and showers. But even in those areas that are built to deal with water, the high pressure can do a lot of harm. Joints and seals are not built for such pressures. They will be ok for regular moisture and water but can be less effective against high pressure.

Should you wear a mask while pressure washing?

In general, you should wear a face mask while pressure washing. The water itself is usually not a problem, but the high pressure can send dirt or other particles flying around. Those can be more harmful to your eyes. Also when you use detergents to get rid of tougher stains, they can be harmful.