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Operations and Management

5 factors of carwash cleaning

These elements work together to
produce clean, dry and shiny.


The main objective for every carwash operator is to produce the cleanest, driest and shiniest cars possible in a timely manner every single time a car is washed. In order to reach this goal, the entire carwash must work in synergy at all times.

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There are five critical factors when cleaning a vehicle: water quality, temperature, mechanical action, dwell time and chemistry. These five factors vary and are not equal at each individual carwash. When one is diminished, one or more of the other factors will need to be increased to obtain the clean, dry, and shiny vehicle. 

Water quality

Water quality can be broken down into two separate sections: water hardness and total dissolved solids (TDS). Water hardness is the amount of calcium and magnesium salts in the water, and it plays a critical role in achieving a clean, dry and shiny vehicle. As a rule, each grain of hardness diminishes the effect of detergents by 5%. 


TDS represents the total concentration of dissolved substances in water and is typically measured in parts per million (ppm). Water high in TDS (above 30 ppm) will leave white spots on the car after the water has dried. Spot-free water is usually considered anything below 20 ppm. 

It is imperative to have high quality water, as no other factor of cleaning can truly offset poor water quality. 


Temperature can be broken into three parts: ambient, vehicle and solution (ready-to-use chemical). 

Ambient temperature is very difficult to control unless the wash bay is completely indoors and temperature-controlled. A vehicle’s temperature can be very hot, especially in warmer climates, so a “cool down” application may help ensure that all chemicals are applied to the surface within a safe temperature range. 


The solution temperature is very important in some carwash models and less important in others. Most friction carwashes apply the ready-to-use solution at room temperature, but some touchless carwashes use heated water to help the chemistry work more efficiently due to less mechanical action being available. 

In addition, extreme cold water will decrease the foaming action of cleaning solutions. Furthermore, most cleaning solutions see a point of diminishing returns somewhere around 120 degrees and may even cause harm to vehicle surfaces at higher temperatures. 

Related: How to prepare a carwash for winter

Mechanical action

Mechanical action is any object or force that is used to remove soil from the vehicle’s surface. In modern carwashes, there are two types of mechanical action: friction and high-pressure water. 


Prep brushes, wraps, mitters, top brushes, etc., represent different types of friction that are used in today’s washes. As a rule, the more friction that one has available, the less important other factors are, except for water quality. 

An alternative form of mechanical action is high-pressure water, which is generally measured in pounds per square inch (psi). Typically, touch-free machines apply high-pressure rinses between 1,000 to 1,200 psi. Chemistry and temperature become very important in touch-free cleaning, as the high-pressure rinse does not equal most friction applications. In order to aid in this process, other factors of cleaning need to work in synergy. 



Time is something that is very limited in most carwashes, but is a very important part of the cleaning process. Dwell time is critical, particularly when utilizing touch-free washing or when cleaning organic matter, such as bugs and tree sap, in any carwash model. 

In general, dwell time increases detergent efficiency and cleaning ability, whereas too little time will diminish efficiency. The timing of your equipment is imperative as well. It needs to work in synergy with the detergent, sealant and drying chemical solutions. This ensures the optimal kinetic interaction between the chemical solution and the soil being removed from the vehicle. 



Chemistry cleaning is the reaction between the solution and soils and the ability of the solution to remove them. Alkaline cleaners are cleaners with a pH over 7, and acidic cleaners are cleaners with a pH below 7. 

As a rule, alkaline cleaners are the best cleaners and can be used as stand-alone cleaners or in conjunction with acidic cleaners. They clean organic soils (bugs, dirt, clays, oils, fluids, tree sap, bird droppings, etc.). Acidic cleaners remove inorganic soils (dirt, clays, salts, rust and oxides). 

It is imperative to use the correct cleaner at the correct dilution ratio and to remember that each chemical has a point of diminishing returns. Always consult with your chemical manufacturer or distributor to ensure the chemicals are being applied at the correct ratio. 


Related: 5 factors of carwash chemicals

Too much chemical can be expensive and very harmful, and too little will result in less than desirable finished products. You should also ensure that your chemicals are safe for the environment and meet all Occupational Health and Safety Administration (OSHA), Environmental Protection Agency (EPA), local and state standards. A reputable chemical manufacturer with on-staff chemists will be up-to-date with current and ever-changing regulations and can provide all documentation needed to ensure compliancy. 

Work with your manufacturer and/or local distributor to make the proper adjustments, as it is imperative that all five factors are working optimally and in synergy. Focusing on these factors is one of the surest ways to increase profitability through customer loyalty. When working together, the five factors of cleaning can produce a clean, dry and shiny car in a very timely manner and can also increase customer satisfaction, retention and sustainability. Happy washing. 


Anthony Shifflett is AVP Eastern Region U.S. with Cleaning Systems Inc. (CSI) – Lustra. 

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