Choosing a good pressure washer can actually be a rather tricky task. This is made more complicated if you are trying to deal with the more complicated cleaning tasks, such as trying to remove stains from vehicles and concrete. Depending on the surface and the type of dirt, each will require a different pressure washer size.
I’ve put this guide together to give you an idea of the best size for the type of cleaning you have in mind.
What Is a Good PSI for a Pressure Washer?
The PSI (Pounds Per Square Inch) rating of your pressure washer usually determines the size of the unit. When you are choosing a pressure washer, the PSI is one first numbers you should look at. This is how you know that it’s got enough power to get the job done, while also being gentle enough not to damage the surface you are cleaning.
Here are some PSI ranges to consider based on the jobs you may be looking to do.
- 1500-2500 PSI: BBQ Grills, outdoor furniture, vehicles, decking, siding, and patios
- 2500-3000 PSI: outdoor furniture, vehicles, patios, concrete, fences, and decking
- 3000-4000 PSI: Large vehicles, boats, sidewalks, driveways, and house siding
- 4000+ PSI: thick materials, and stripping paint or graffiti removal
The larger PSI units can do the jobs of the smaller PSI units with one caveat. Delicate surfaces can’t handle high PSI ranges. To deal with those, the larger units need the ability to adjust their PSI to a lower level. I think it’s safe to say that the higher the PSI rating of your unit, the easier it is to remove dirt.
What Is a Good GPM for Pressure Washer?
While PSI is a very important factor, there is another number that comes into play when determining the size of your pressure washer, and this is GPM (Gallons Per Minute). This number is all about how much water will be used per minute, while PSI is the brute force. This number is responsible for washing away the debris while you are cleaning.
The higher the GPM, the more water your pressure washer will use per minute, while a low GPM means less water will be used. Low GPM units are perfect for small cleaning jobs where you want or need to save on water.
The biggest benefit of having a high GPM is the speed at which cleaning will be completed—the more water that is expelled, the faster the dirt is removed. For residential use, you can go from as little as 0.8 GPM all the way up to as high as 4.0 GPM.
If you are only going to use your pressure washer every now and then, perhaps to clean the car, then a lower GPM rating is perfect. A high GPM rating is really only required when you are trying to clean a large area for general residential cleaning, as 1.5 or 2.0 GPM unit is perfect.
If you want to save water for money reasons or because you are environmentally conscious, then a lower GPM model may be for you, though you do need to factor in the time taken. If you have a 5 GPM machine and with it, it takes 2 minutes to clean something, but by using a 2 GPM machine, it takes 5 minutes, they’ve both used the same amount of water.
Also, you need to factor in what you can supply. Can your hose provide 5 GPM? A quick way to find out is to turn your hose on full, take a 5-gallon bucket, start a timer, and start filling the bucket. After 60 seconds, remove the hose from the bucket and measure how much water is in the bucket. If you filled it to 3 gallons, then the max you can support is 3 GPM, if you filled the 5-gallon bucket then it’s 5 GPM, etc.
What Size Do I Need for Different Types of Surfaces?
I’ve mentioned above the types of surfaces and the recommended PSI rating. But in this section, I’ll go into further detail about the typical items and surfaces you’ll be cleaning with a pressure washer.
However, depending on the PSI rating, you could cause dents, though that is highly unlikely, what’s more, likely to happen, and something you really should worry about is accidentally stripping the paint of your car. Certain pressure washers have a PSI rating high enough to wash off graffiti from concrete or remove paint from a fence. So what do you think will happen to your car?
Now, these larger pressure washers may not strip all the paint off. Instead, they’ll chip away at the paint in bits and pieces. This won’t just make your car look awful but raw metal, water, the elements. That’s a recipe for rust.
So I suggest to protect your car, that it makes sense to use a pressure washer with a PSI rating within 1200 PSI all the way up to 2100 PSI. Different cars have different paint mixes, some are harder than others, and some love to scratch, so I suggest starting with the lowest setting and keeping the spray nozzle at least 18 inches from the paint. If the lowest PSI setting is too low, you can increase it. Though I suggest not going higher than 2100 PSI. As for GPM, anything up to 2.0 will be sufficient.
2. Wood Furniture
Using a pressure washer to clean wood furniture just makes sense, it can get into all of the nooks and crannies and will help you get rid of mold and mildew.
You can use the same pressure washer you used on your car. Still, I actually suggest going slightly larger than the one you used on your car, as the unit needs to “dig” deep into the surface to remove ingrained dirt. To do that, it needs strength, raw power.
Unlike cars, most modern types of wooden furniture tend not to have any paint of finish that you are at risk of removing or scratching. This is why an electric pressure washer with a PSI rating of around 2500 PSI, and a GPM rating of around 2.0 GPM is a fantastic choice. This will be able to wash away all of those stubborn stains and any grime. Say goodbye to sticking model from those hard to reach crevices.
Though while wooden furniture is quite durable and won’t tend to chip when it’s pressure cleaned, you shouldn’t go for the high-pressure red nozzle or any of the smaller ones. If you do, then you are at risk of poking dents into the surface of the wood. Instead, I suggest using something around 25-degrees.
3. Concrete Surfaces
Finally, we’re onto concrete surfaces. These are typically the floors of your patio, your garage, and your driveway. Concrete is a very hard and durable surface. Stronger than wood and your car. It’s also a porous material. So to clean it, you need a much larger PSI rating.
Typically I suggest using a gas pressure washer as these are perfect for cleaning concrete. Though if a gas pressure washer isn’t for you, then a smaller unit will do a relatively good job, it may not give a perfect result, and you will be working on it for a while. But it’s doable.
The size of your pressure washer will depend on how thick your concrete slab is. An average concrete slab for a patio or driveway is around 8 inches, so you would be looking for a PSI range of 3500-4500 PSI.
Concrete flooring benefits from a PSI rating of 4500 PSI and 2.0 GPM. These pressure ratings are strong enough to penetrate deep into the porous slab and lift out stubborn grime and dirt while not being strong enough to damage the concrete.
So the answer to the question “what size pressure washer do I need” isn’t so simple, there are a few questions you need to ask yourself. Firstly, what are you going to clean, are you working with sensitive surfaces? Are you looking to clean your car and your concrete because if so, you can’t use the same pressure washer, not unless you can adjust the pressure.
With pressure washers, bigger is not always better, bigger brings more risk in terms of damage to surfaces and yourself and others if accidents happen. Plus, why pay extra for the extra PSI & GPM if you don’t need it? Stick to the size that’s perfect for the jobs you have in mind.