How To Clean Siding Without A Power Washer

Pressure Washers Today I was wondering, what's more important in a pressure washer PSI or GPM? After some research, I discovered that both are equally important, depending on the application that you need the pressure washer for, and how much time you want to invest in cleaning.

The PSI tells you how quickly the water is being pushed out of the washer and the GPM tells you how much water is hitting the surface area. These two things combine to create a deep cleaning solution for a dirty project. Here is how it all comes together.

What Is PSI in a Pressure Washer?

When looking at a pressure washer, one of the first things you will notice is a reference to the available PSI, which stands for Pounds per Square Inch. An example would be 1,800 PSI or 2,000 PSI. Extremely high powered commercial pressure washers can have a PSI that is upwards of 5,000 or more.

The PSI rating for a pressure washer tells you the force with which the water is coming out of the machine (the pounds per square inch of pressure behind the water coming out of the machine). It gives you an indication of the cleaning power of the machine. The higher the number, the more cleaning power it will have.

What Is GPM in a Pressure Washer?

The gallons per minute of water coming out of the machine (the GPM) are what wash the debris away after the cleaning is done. A higher GPM means that more water is pushed out of the machine at a time and a lower number means less water is coming out.

The main benefit of having a higher GPM is speed. The more water you have washing away detergents and debris (the GPM), the faster the job gets done.

For most residential models, the range of GPM may be as little as 0.8 GPM and as much as 4.0 GPM.

When buying a pressure washer that you will only use occasionally around your home, the lower end of the GPM will probably be sufficient for your needs. You only need the higher GPM when you are cleaning very heavily soiled areas. A GPM of 1.5 to 2.0 would handle most cleaning jobs around the home with no problem.

What Is CU in a Pressure Washer?

CU stands for Cleaning Units. This is a way for you to gauge how quickly your cleaning projects will be finished based on the PSI and GPM of your machine.

To find the CU of your machine, if it is not listed on the product, multiply the PSI by the GPM. For instance: you have a 2,000 PSI pressure washer that operates at 4.0 GPM. The CU will be 8,000. (PSI x GPM = CU). If you have a smaller pressure washer, 2,500 PSI at 2.0 GPM the CU will be 5,000. The higher the CU, the faster the cleaning process will go.

Therefore, even though the PSI is higher with the second example, the first will still get the job done faster. However, it is important to remember that the lower PSI may not be ideal for tougher cleaning projects. In this case, even though the 2,500 PSI machine may take longer, you may get a deeper cleaning from it overall. This is where trial and error may be required for the best cleaning of the surface that you are working with.

The good news is, you don't need to purchase a different machine for every cleaning project around your home. You can often change the PSI rating by simply choosing a different nozzle tip. Some pressure washers even include tips that are different sizes to make it easy for you to increase or decrease the PSI to meet your specific needs.

What PSI and GPM Are Best for Residential Pressure Washer Projects?

PSI

When you are searching for a pressure washer for your home, it's probably preferable to stick with the lower end of the PSI scale. One reason is because of the price. Residential washers are generally only used occasionally and don't warrant paying the high price of a heavier commercial machine.

Also, a PSI of somewhere between 1,200 and 2,000 is perfect for most projects around the home. This pressure is strong enough to clean but unlikely to cause damage to your automobile, boats, bicycles, and other areas.

It can also be used on siding or wooden areas. Bricks can be deep cleaned, and you do not have to worry about chipping even painted surfaces if you are careful.

If you have a lot of heavily soiled areas, you can go a little more powerful. Up to 2,900 PSI is reasonably safe, but you will want to test areas before you apply the tip too close.

GPM

Smaller pressure washers (1,000 PSI to 1,700 PSI) will have a low GPM. An electric pressure washer in this PSI range is typically going to be around 1.5 GPM.

A gas powered pressure washer with a higher PSI may be as much as 2.8 GPM. There are exceptions to every rule, but if you choose a pressure washer that provides a GPM in these ranges you should be completely satisfied by the results.

What PSI and GPM Are Best For Commercial Pressure Washer Projects?

PSI

Commercial pressure washers are designed to handle more frequent, deep cleaning projects. Anything above 3,000 PSI is generally considered a commercial pressure washer. Their PSI can go as high as 6,900, and is generally used on heavily soiled parking lots, warehouse floors, and heavy equipment.

If the PSI goes above 7,000, it is an extremely powerful cleaning machine and should never be used around anything you would have at home. They are generally used for cleaning bridges or very heavily soiled backhoes and such.

GPM

The GPM of a commercial pressure washer can be up to 4.0 GPM. This is ideal for deep cleaning concrete, stripping paint or graffiti, and more. This is not to say that a residential pressure washer cannot use 4.0 GPM, but it is something that is not commonly seen.

Final Thoughts

If you have too much PSI, you risk major damage to your personal property. If you don't have enough PSI, you may not have enough power to get the job done.

If you have too much GPM, you could end up wasting water on small jobs. If you don't have enough GPM, it may take you forever to finish the job.

When it comes to "What's more important in a pressure washer PSI or GPM?" I would have to say that it is both. If you do not have enough of one or the other, your pressure washer may let you down when it comes to even the most basic of cleaning projects.

For ideas on pressure washer tasks, check my articles on "Best Pressure Washer For Vinyl Siding" or "What Size Pressure Washer Do I Need To Clean Concrete".