What size pressure washer is needed for a cleaning task can be summed up as follows: for pressure washing brittle surfaces that can be damaged easily such as grills, outdoor furniture, and cars, a PSI between 1000 and 2000 is appropriate. Pressure washing concrete surfaces, patios, decks, and pools requires a PSI in a range of 2000 and 3000. Heavy-duty cleaning tasks such as cleaning industrial equipment and bulky grease stains should be done using 3500 PSI and above.
How to choose the right PSI for a cleaning task is discussed in detail below.
What Is a Good PSI for a Pressure Washer?
The PSI for your pressure washer is one of the general determinants of the size of your unit. When determining the PSI (pounds per square inch) of your device, you need to make sure that it has enough power to get the job done, but that it’s also gentle enough not to damage the surface (or yourself). Here are the recommended PSI for pressure washer, depending on the surface that you are trying to clean:
- 1500-2500 PSI: grills, outdoor furniture, vehicles, and patios
- 2500-3000 PSI: outdoor furniture, vehicles, patios, as well as dirt from fences and docks
- 3000-4000 PSI: large cars, boats, sidewalks, driveways, house sidings
- 4000+ PSI: thick materials, paint and graffiti removal
It is safe to say that the more PSI your unit has, the more pressure you will get – and the easier it will be able to get into thin dirt. Bear in mind that a high PSI unit can do a lot of damage if you are using it on fragile surfaces.
What Is a Good GPM for Pressure Washer?
The PSI is not the only important factor when determining the size of your pressure washer – you also need to give a close look to the GPM (gallons per minute). This needs to be done, as the GPM is responsible for washing away the debris after you’ve finished cleaning.
A high GPM means that the pressure washer will push more water over one minute, whereas a lower PSI means that less water will be used. Low GPM units are a great option for those that have small cleaning jobs to do and want to save on water.
That being said, a benefit that comes with having high GPM is the speed of cleaning. The more water the unit pushes out, the faster it will be for you to wash away dirt and debris. For residential use, you may benefit from pressure washers with a GPM as low as 0.8 and as high as 4.0.
If you are only planning to use your pressure washer now and again, then a lower GPM is exactly what you need. A higher GPM may only be required when you are trying to clean an overly solid area. For general residential cleaning, a 1.5 or 2.0 GPM unit might be more than sufficient.
There are also units with a higher GPM that you may benefit from, but that might cause you to use quite a lot of water. If you want to be environmentally conscious or save on your utility bill, this might not be a good choice – especially if you have a smaller area to clean, for example.
What Size Do I Need for Different Types of Surfaces?
As mentioned, each surface type might require a different size. Here is what you need to focus on, based on the typical items and surfaces that are cleaned with pressure washers.
Many people buy a pressure washer so that they can clean their car with it. So, while you do not particularly have to worry about creating dents in your car with your pressure washer, you should worry about the paint coming off. After all, certain pressure washers with a high PSI were made to wash off graffiti or the paint off the fences – so what do you think this can do to your car?
Granted, a bigger pressure washer might not make the whole paint come off. Instead, it will chip away in bits and pieces. This way, not only will your car look bad, but it might also encourage rust spreading from where the paint has chipped.
For this reason, to protect your car, you might want to use a pressure washer going from 1200 PSI to 2100 PSI. Since some cars and paint types can scratch much easier in comparison to others, you might want to start at the lowest setting and work your way up if it doesn’t seem to be delivering enough power. You shouldn’t go higher than 2100 PSI, however – and a GPM of 1.2-1.5 is more than sufficient.
2. Wood Furniture
Pressure washers are a good way to clean wood furniture, as they will help you get rid of mold and mildew. For that, you will need a slightly bigger PSI than you would normally require for your car – the unit must “dig” deeper into the dirt. It needs enough strength to spray off those buildups – all of which have already made their way through the wood.
Unlike cars, most modern types of wood furniture don’t have any paint or finish that you risk scraping off or scratching. This is why you might want to get an electric pressure washer with an average PSI of 2500, and an average GPM of 2.0. This should be enough to wash off the stubborn grime and the sticky mold from the unreachable creaks of your furniture.
Bear in mind that while wooden furniture is quite durable and won’t chip from this kind of pressure, you shouldn’t go for the smaller nozzles. If you do so, you will only risk poking dents in your furniture. Make sure that you go for at least a 25-degree nozzle so that you spread the pressure out a bit.
3. Concrete Surfaces
Last but not least, there are concrete surfaces – generally on the floors of our patio and our driveway. Considering that concrete is a very hard surface and stronger in comparison to wood or the surface of your car, you will require a much stronger PSI – a powerful gas pressure washer would be great for this job. Granted, a smaller PSI unit should also work, but at the same time, the cleaning process will be lengthened.
That being said, the size of your pressure washer will also depend on how thick your concrete slabs are. For example, the average concrete patio or driveway will have slabs of around 8 inches, so the average size of your pressure washer should be around 3500-4000 PSI.
Typical concrete flooring will also benefit from a 4500 PSI unit with a 2.0 GPM. The pressure point is strong enough to wipe away stubborn grime and dirt, yet it won’t be strong enough to cause any actual damage. To be sure, get a pressure washer with a setting between 3500 and 4500 PSI, working your way up from the smallest setting if the pressure is too small.
So, to answer your question “what size pressure washer do I need,” you must also consider a few variables. First things first, you need to determine exactly what you want to wash. Certain surfaces are more sensitive, and you cannot use the same pressure washer to clean your concrete and then move onto your car – not unless you can adjust the pressure.
When it comes to pressure washers, bigger is not always better. Not only do you risk damaging the surface, but you’ll also be paying needlessly for something you won’t use. Stick to the size that you need for what you’re washing.