How To Clean The Car and Garage Floor With a Pressure Washer?

I recently bought a 2600 PSI gas pressure washer but I haven’t used it yet, I plan on using it today but I have a couple of questions. I have a foam lance (a foamer gun) for washing cars,what PSI should I use when the foam gun is attached to it to wash my car? Also, my garage doors are dirty, what psi should I use to clean them and avoid chipping the paint on them? High pressure nozzles can strip off the paint. It can also remove the clear coat. If you use higher pressure keep the nozzle far away from the surface. Remember too these high pressures can cut through skin and even cut fingers and toes off.

How To Choose Best Pressure Washer For Car?

Tips choose the appropriate pressure washer and nozzle for car

When washing your car, it’s important to use a pressure washer with the appropriate power (PSI: pounds per square inch) and water flow (GPM: gallons per minute). The higher the PSI, the more force the water will have as it leaves the tip of the washer. The higher the GPM, the more water the washer will release.

Cleaning Units represent the combination of force and amount of water a pressure washer can produce. This is demonstrated in the equation below:

PSI x GPM = Cleaning Units

1500PSI x 2GPM = 3000 cleaning units:

Tip: Washing a car with a pressure washer requires around 1,900 – 2,800 cleaning units.

Note: Pressure washers are far more efficient than garden hoses and use less water. See the table below to compare cleaning units between a hose and a pressure washer.

You can purchase both electric and gas-powered pressure washers. In general, gas pressure washers have a much stronger cleaning capacity and are too strong for light jobs, such as washing a car or truck. In order to avoid damaging your vehicle, it is better to use an electric pressure washer set at the appropriate PSI.

There are a number of different types of nozzles to choose from. Using the correct size is important so that your car is cleaned effectively and without damage to the paint job.


Choose a pressure washer with the appropriate pressure level

Choose a pressure washer with a setting of 1200 – 1900 PSI. It’s safe to use for cars, so you won’t need to worry about damaging the paint on your car. Experts recommend using a pressure washer with 1.4 – 1.6 GPM.

How To Cleaning Your Car With A Pressure Washer?

Rinse off the top layer of grit and grime.

If you’re using a machine with a variable jet spray, adjust it to a spray of approximately 5-8cm wide, so it’s strong enough to clean the car but won’t damage the paintwork. You will need to use a slightly wider and less powerful setting for the windows, lights and other fragile areas.

Apply a detergent.

Set the pressure washer nozzle to the widest and least powerful setting – or remove it altogether – to coat the entire car in a layer of detergent. Let it work its magic for a few moments, but don’t let it dry or you’ll be left with blemishes that will have to be buffed out later.

Loosen the most stubborn dirt and grease.

Use an attachable car brush to make the job quicker. If you’re using the same one to clean the wheels and wheel arches, as well as the paintwork, do the wheel areas last as there’s more chance of the brush picking up small stones and grit from around the wheels, and you don’t want to be rubbing these against the paint. Rinse the brush thoroughly once you’ve finished using it to make sure all grit is removed.

Rinse the car off with a high-pressure jet setting.

Again, using a slightly stronger setting for the paint than the glass areas. If you don’t have a variable nozzle to adjust the power and width of the spray, just stand further away from the car – one metre should be a safe distance to prevent any damage.

Take care with your pressure washer

  • Don’t ever use a rotary (or tornado) nozzle attachment when cleaning your car as it will be too strong and could damage paintwork.
  • Watch out for the initial burst of water that comes out of the pressure washer when you first turn it on. There can be a strong initial spray, so point the nozzle at the ground first.
  • Try to pressure wash the car on concrete rather than on a gravel driveway to avoid the possibility of stones flying up and hitting the paintwork.
  • Don’t use a strong spray on areas where paint is chipped as it could strip more paint away.
  • Don’t use a high spray setting on old tyres, as it has been known to make them explode.
  • Never spray the engine bay, the boot or the interior – unless you fancy buying a new car. It’s also worth checking all the windows are closed properly.
  • Don’t point the spray directly at panel gaps for too long as these areas will be most susceptible to leaks. It’s worth checking the interior after spraying to see if any of the doors have leaking seals.

2400-2500 psi will work around the home but will strip paint off your car if you’re not careful and intended to use it for washing the vehicle. A 1300psi is perfect for the car, strong enough to clean the wheels (held fairly close) but not enough to damage the paint with an inadvertent slip but won’t do much cleaning around the house.

There are other features to look for beside the rated PSI (which is often overstated BTW or measured with the smallest possible orifice). Ceramic pumps are much better than steel. Also, a lot of the low cost gasoline washers do not have a pressure bypass feature so if you are not going to use it for several minutes, you have to shut it down which can get tiresome. You also want one that will let you use the high pressure side when shooting detergent, a lot of them only draw it on low pressure usage.

As someone else mentioned, get at least 30 feet of hose, a proper storage feature (preferably windup) for the hose, an adjustable nozzle rather than having to constantly change tips. Good units will come with two wands, one is adjustable and the other uses tip changes for a wider choice.


How To Clean The Garage Floor With a Pressure Washer?

Pressure washers come in both electric and gas engine models and each model is rated for how much water pressure they produce.  This pressure is measured in pounds per square inch or PSI at the tip of the nozzle.  As well as being rated for PSI, they are also rated for water flow which is how much water they produce in gallons per minute or GPM.

So what kind of pressure washer should you use for a garage floor?  For a bare concrete garage floor you want to rent a gas powered pressure washer with a minimum rating of 3,000 PSI and a water flow rate of 3 GPM or more.  Anything less will not be as effective and will take longer to get the job done.

The reason for this is that dirt encrusted and oily concrete does not clean as well with anything rated for less than 3,000 PSI.  The minimum 3 GPM will also enable you to work quicker because you won’t be pushing around a pile of dirt and debris due to a lower flow of water.

You can usually rent these from $45 – $65 a day depending on where you live and the rental store you are dealing with.

Electric pressure washers are not a good option for garage floors as they rarely rate over 2,000 PSI.  They are fine for general purpose cleaning but not for heavy duty jobs.

Once you have selected a pressure washer to rent, make sure you know how to start it before you take it home.  Start it yourself at the rental facility to ensure that it runs correctly and to ask any questions about the operating procedures that you find confusing.

How To Pressure Washer a Garage Floor

Be sure to wet down the floor first before cleaning with the pressure washer.  This will eliminate streaking that can occur in the concrete after it dries.  Sometimes it’s best to work in sections.

Pretreat any oil or grease stains with a strong concentrate of degreaser.  It helps to scrub it in with a deck brush if you have one.  Be sure to let the stains soak for 15 to 20 minutes without drying out.

While your stains are soaking, you can turn your attention to the rest of the floor.  In order for a pressure washer to work best at cleaning the garage floor you need to soak the remaining concrete with a degreasing solution as well.  Many pressure washers have a separate reservoir to add a degreasing product.  We like Simple Green Concrete and Driveway Cleaner.

While your pretreated stains are soaking, add the degreaser to the reservoir of the pressure washer and select the low pressure tip for the cleaning wand.  This is usually the black tip.  Start the pressure washer up and apply the degreaser to the garage floor.  It should create a nice foamy solution.  Make sure to turn off the valve that allows the degreaser to enter the hose when you are done.

If your pressure washer doesn’t have a reservoir for a degreaser, just mix up a strong solution in a bucket and spread it out on the floor.  Either way, let the degreaser soak for 15 – 20 minutes without drying out.  Spray some water on the surface if necessary to keep it wet.  Once the concrete has soaked you can start pressure washing the garage floor.

elect the yellow 15° spray nozzle.  This works best for heavy cleaning in most areas.  If the floor isn’t too dirty, you can try the green 25° nozzle as it will cover a larger area but uses less force.  The key is to keep the tip of the wand 6” -12” from the surface while pressure washing the concrete.  Always keep the wand moving and don’t linger in one spot too long or you can possibly etch the concrete.  A deliberate and methodical pattern works well and will keep you from missing any areas.

Pay particular attention to any oil spots that you have pretreated.  Sometimes it may take a second application to get them completely clean.

Safety Tips And Tricks

Pressure washers can be dangerous and cause bodily harm if you are not careful.  Never pressure wash in your bare feet.  The high pressure spray can rip the skin right off the top of your feet.  Wear an old pair of shoes or rubber boots.

Never run your hand through the spray to check the pressure.  It will damage your hands immediately.  It’s a good idea to wear eye protection as well.

We recommend taping up some cheap plastic drop cloths to the lower 3 ft. of your walls to protect electrical outlets and finished drywall.

Because pressure washers actually use less water per minute than a regular hose, it’s a good idea to hose down your driveway before you start.  The dirty water that is flushed from the garage is fairly concentrated and this will prevent the contaminants from the garage getting deposited on your driveway.

To speed up the cleaning process and get the best results for extremely hard to clean spots you can use a special rotary tip called a turbo nozzle.  They work by spinning a 0° spray pattern in a 4” to 8” circle at 3000 RPM’s.  This allows the 0° spray to attack the concrete from various angles at once which will reduce the cleaning time considerably.

Most rentals don’t come with a turbo nozzle so you may have to ask for it as an accessory or purchase it separately.

Lastly, don’t forget to purge your hoses and the pressure washing unit of air before you start it up and make sure it’s set on level ground.  Depending on the unit you have, some have a low oil level engine shut off switch that may be triggered if it is sitting at an angle.

Using a pressure washer on your garage floor is not hard.  The key is choosing the correct one to get the best outcome.  Don’t use something less just to save a few bucks on a rental.  If you follow these tips, you should be very satisfied with your results.

I have one with a 13hp honda engine. I think 4000 psi pressure washer is best for clean the garage floor , 4 gpm, or something like that. It will take the siding right off of a house if you want it to. I often use it full power to clean sidewalks and the dock and wall on the pond behind my house. I’ve taken it to the family farm, and cleaned up muddy tractors with it.

However I often turn the engine down to a lower throttle setting and it works fine for more delicate stuff. I can wash cars at idle.

It’s overkill for most jobs, however I’ve used it a ton over the years. My father in law had one of the karcher electrics to clean the siding on his home in Florida. I used it once and it was a bit wimpy, but did the job.

If you do a lot of projects, I would recommend one with gas – a 5hp model would do most jobs. One thing to consider is the length of the hose – I’ve seen cheap ones with 15 ft hoses – which is not nearly enough. I put a hose reel with 150 feet of pressure hose on mine. That way I can do just about anything around my house.

For home/cars, anything over 3000 PSI pressure washer is pretty overkill.