Car Wash: How Exactly Does It Work? – 13 Step Process Explained

We take many of the technological marvels we use in our daily life for granted, and car washes are one of them. We drive our 4,000-pound (1,814 kg) vehicles onto a conveyor belt that magically cleans all the dirt and debris. Still, have you ever wondered exactly how car washes work? 

Car washes work by moving your car along a conveyor belt with different stations. Each of these stations is responsible for lathering soap, scrubbing, rinsing, or drying. The vehicle is moved automatically through each station, resulting in a clean car after going through the whole system.

Although these steps may sound simple at first, a lot is going on behind the scenes at an automatic car wash center. Keep reading to learn more about how car washes work and what you can expect from yours. I’ll also tell you about some of the types of car washes and when one might be better than the others. 

How Does a Car Wash Work?

Car washes work by pulling a car on a conveyor belt through a multi-step cleaning process. This process includes high-pressure washing, foam application, scrubbing with brushes if it is a friction car wash, washing again, blow-drying, and applying protectants like wax.

Although different car wash centers will offer different pricing tiers, you can usually expect even the most basic package to include washing, foam, scrubbing, and rinsing. You can expect them to try to upsell you with add-ons such as blow-drying, waxing, and interior cleaning. 

What Are the Steps of a Car Wash?

Going through an automated car wash is usually an enjoyable experience. You have to pull up, park where they tell you to, and let the machine do the rest. However, many intricate steps go into a car wash. 

Here are the steps of a car wash:

  • Placing the car on the conveyor track.
  • Pre-soaking the vehicle.
  • Foam application.
  • Scrubbers or wrap-around washers scrub the car.
  • High-pressure wash. 
  • Undercarriage wash applicator.
  • Rinsing.
  • Wax application.
  • Final round of scrubbing.
  • Final rinse.
  • Mitter curtain.
  • Hot air drying. 
  • Interior cleaning.

Not all car washes include all of the steps mentioned above. Most will try to upsell you with some final measures, which are not considered essential to a car wash. So, let me walk you through each step and tell you what you can expect from them. 

Placing the Car on the Conveyor Track

The first car wash step is placing your vehicle on the conveyor track. Most car washes will let you drive directly onto the conveyor track. Then, you will move onto the correlator, which is a device that helps move the car to the precise location your tires need to be in. 

Once you’ve driven onto the correlator, an attendant or machine will tell you to turn your vehicle off and put it in neutral. Shifting gears will allow the conveyor belt to move your car into the tunnel and through each washing station. 

When your car is ready to go, the conveyor will move it through two infrared beams at the very entrance of the tunnel, called the eyes. These eyes will let the system know that a car has entered the tunnel and kick off the rest of the washing sequence.

Pre-soaking the Vehicle

Once the washing sequence has begun, the first thing that will happen is the pre-soak. During this phase, a rinse arch containing several nozzles will spray water on the vehicle to gently rinse off any dirt before applying heavy detergents.

Some rinsing arches also include a gentle cleaning solution in the pre-soak water. This solution will help chemically break down some of the harsher dirt and debris on the car. 

Foam Application

After the pre-soak, the next step in a car wash is the foam application. This foam contains the detergents that will be doing all the heavy cleaning for your car. Most car washes use foam applicators for this step, wide nozzles that spray foam directly onto the vehicle.

Most car washes use a type of detergent called snow foam, which helps break down and trap any dirt, grime, bird poop, pollen, or any other substance on your car. They also help lubricate your vehicle, making it easier for the scrubbers to glide over your car without scratching the surface.

Scrubbers or Wrap-Around Washers Scrub the Car

This stage is the part that most children and pets either love or loathe. The scrubbers are tall, cylindrical columns covered in soft cloth strips. These machines spin rapidly, at about 100 rpm (revolutions per minute), which allows them to knock off any dirt or unwanted substances off the surface of your car.

Different car washes will have anywhere from two to eight scrubbers in the entire system. A car wash usually requires an even number of scrubbers on each side of the car, giving the vehicle an even scrubbing from both sides.

Most car washes also include a mitter curtain in the scrubbing phase. These curtains have long pieces of soft fabric that will help scrub the roof of your vehicle. More modern mitter curtains also move up and down, helping clean the whole upper part of your vehicle.

Some car washes may also have wrap-around washers in addition to or in place of scrubbers. These washers look very similar to regular scrubbers, except they hang from a small crane that allows the machine to move the scrubber around the vehicle. This moveable arm will let the washer clean the vehicle’s front, sides, and back. 

For a quick demonstration of how wrap-around washers work, watch the following YouTube video:

High-Pressure Wash

Once the brushes and curtains scrub your car, it’s time for the high-pressure wash. This step consists of rotating water jets meant to wash off all the foam and any debris that may remain on your car.

This step is the most water-intensive in the entire car washing process, as each car that passes through the system can consume up to 400 gallons (1,500 liters) of water. 

If you are concerned about the environmental impact of washing your car, do not worry. I’ve covered the best water conservation tactics available in the last section of this article, so rest assured that a car wash can be eco-friendly. 

Undercarriage Wash Applicator

The undercarriage wash is an optional step that not many car washes include. If you live in a place where there is a lot of snow during the winter, your local car washes may have one of these. 

An undercarriage wash applicator consists of water nozzles that shoot water and a cleaning solution on the bottom of a vehicle. These can remove salt and mud, keeping all the metal parts underneath your car clean and rust-free.


After the high-pressure washing, your car will likely go through another rinse arch. A car wash will typically include at least three rinsing arches, helping keep the car clear of any dirt or foam residue through every step of the system. 

The rinsing immediately after the power wash helps ensure that the car is completely clear of any detergent or dirt before entering the final stage of the washing sequence. Depending on your package, you may or may not be moving on to an add-on cleaning service, such as wax application and air-drying.  

Wax Application

One of the final stages of a car wash is the wax application, which usually shoots from a wax arch. These arches look very similar to rinsing arches, except they shoot car wash wax instead of water.

You should know that the wax used during this step is different from what you would apply yourself by hand. This wax works on the entire surface of your vehicle, including the body, glass, and metal. Car wash wax generally includes:

  • Carnauba wax. Also known as the “queen of waxes,” this is the main active ingredient in your car’s wax.
  • A blend of other oils. These additional oils vary, but the mixture generally includes beeswax and other natural oils.
  • Petroleum distillates. These petroleum byproducts help the wax spread more evenly along the vehicle surface. 

This blend of wax gives a decent amount of protection to the entire surface area of your car. However, manual body wax will always be more effective than car wash wax. Some car wash centers offer manual waxing as an add-on after the vehicle has gone through the car wash tunnel. 

Final Round of Scrubbing

The car will go through a final round of scrubbing after applying the wax. However, this final scrub usually only happens when foam wax is applied instead of liquid wax. This step will use dry or slightly moist scrubbers to scrub off any excess foam wax from the vehicle, leaving a streak-free shine.

Final Rinse

Whether the car wash uses foam or liquid wax, cars will usually go through a final set of rinsing arches before hitting the drying station. Drying is the last section of the washing process, and it will rinse off any leftover soap, wax, detergent, or foam from your vehicle. 

At this point, your car should be immaculate, so this rinsing arch should be rinsing off any excess soap or wax. 

Hot Air Drying

The last step in a car wash is usually the drying station. Depending on the package you purchased, your car wash may or may not include hot air drying. 

One of the downsides of skipping this station and just heading straight out is that you may have water stains on your car. 

If you don’t get a hot-air drying section in your car wash, residue from the water may leave a noticeable dipping or streaking pattern, especially if your car is a dark color like black or dark gray. 

A hot air drying station essentially works as a giant blow dryer. Car wash dryers blow hot air onto your vehicle to both evaporate and blow off the leftover water from the surface of your car. Going through this step is very important to prevent unwanted water stains on your vehicle.  

Interior Cleaning

Most gas station automatic car wash services don’t include interior cleaning as it’s a step that is impossible to automate. However, if you’re going to a dedicated car wash center, they probably offer interior cleaning as an add-on or in their packages. 

Interior cleaning usually involves vacuuming the seats, carpets, and interior walls of your car. They usually also include cleaning the windows from the inside and using a towel to hand-dry the vehicle to prevent any water stains.

Some car washes also offer additional interior cleaning services, like cleaning the center console, wiping down interiors, and using air fresheners to scent your vehicle. If you have any unusual cleaning requirements (like a spill), you may also request that they clean it up at this stage. Depending on the spill’s magnitude, they will usually assess the situation first and give you a quote. 

How Does a Friction Car Wash Work? 

A friction car wash involves using cloth, sponges, or other fabrics to scrub your vehicle gently. These types of car wash use modern technology to quickly move a cleaning fabric over your car to simulate scrubbing. 

Friction car washes are among the most common car washes in the United States. Although modern technology makes the likelihood of scratches very minimal, some skeptics opt for touchless car washes out of fear that the cleaning fabric will scratch or damage their vehicles.

How Does a Touchless Car Wash Work? 

A touchless car wash does not involve physical contact with your car, except for the water and cleaning solution. These car washes do not include any scrubbing whatsoever, which can help protect your vehicle’s paint coating.

Touchless car washes are an excellent option for those with delicate vehicles, such as luxury cars or vintage cars. Since this type of car wash does not involve using any cloth or fabric, it will minimize the likelihood of scratching or wearing out your car’s paint. 

However, they use harsher chemicals since there is no physical contact with the vehicle besides the water and the cleaning solvents. These chemicals may be too intense for some paints and coatings. 

Can A Car Wash Be Environmentally Friendly? 

A car wash can be environmentally friendly if it follows efficient technologies for wastewater treatment. The best practices for car wash wastewater treatment include coagulation and absorption, membrane-based technologies, electrochemical, and combined systems. 

According to a research study published by the US National Library of Medicine, the most effective wastewater treatment for removing pollutants from car wash wastewater involves combining one or more systems. Specifically, combining membrane-based filtration technologies with coagulation systems proves to be the most effective way to clean and filter car wash wastewater.

Ask your local car wash centers about their wastewater treatment strategies. If you’re afraid that a car wash will waste too much water, call ahead and see what options they have for mitigating the environmental impacts of your wash. 

If they do not have any wastewater treatment protocols, you can let them know that you will not be choosing them because of their lack of environmentally-friendly practices. 

Key Takeaways

  • A car wash works by moving a car along different stations on a conveyor belt.
  • Car washes generally include rinsing, scrubbing, washing, waxing, and drying.
  • Your car wash may also offer an interior wash after the car has gone through the automatic wash.
  • Friction car washes include the use of soft fabric to clean the vehicle.
  • Touchless car washes only use water and cleaning solutions.
  • A car wash can be environmentally friendly by using combination wastewater systems.


Chemical Guys: How Do Foam Cannons Work?

Cars Direct: ​​Car Wax Formula: Understanding What It’s Made of

CDC: Petroleum Distillates

National Library of Medicine: Efficient technologies for carwash wastewater treatment: a systematic review

Car Wash Forum: Rotation Speed of Side Brush

Jan-Lucas Ganssauge
Jan-Lucas Ganssauge