Balancing Your Tunnel to Maximize Performance and Profit  

For maximum performance and profitability in your tunnel it is important that you have an understanding on how your equipment and chemistry work together to clean a vehicle. Using too little product might save you money at the cost of return customers. Using too much product will not necessarily clean the vehicles any better than using the proper amount yet will unnecessarily increase costs. Running your conveyor too fast may cause cleaning issues as well as staffing concerns. Running your conveyor too slow may increase chemical costs but not cleaning efficiency. The right selection of chemical products and friction media may improve cleaning quality without increased cost. Understanding the basics of balancing or tuning your tunnel is essential to maximizing your potential as an operator.

In the today’s market there are three basic types of tunnels: friction, touch free and hybrid. Each type has their own need for a chemical balance for the best performance. Many older and some of the newer washes are set up as a standard friction wash. In the late 70’s and early 80’s we saw the development of the touch free tunnel wash. The ultimate effect of touch free tunnels was an increased awareness of the importance of detergency in the wash process, even in friction units. Today, with the rise of closed cell media use in friction units and the shortening of conveyors, the hybrid wash, which combines the best of both worlds – touch free and friction - has created the need for even more efficient detergency in the wash process.

An important aspect of balancing any tunnel is conveyor speed. For years there has been a never ending debate in the tunnel industry regarding conveyor speed. Generally operators tend to run conveyors at a much higher rate than necessary. It should be set to handle the amount of cars that are normally done at the wash if it has been properly staffed. The other factors involved are the day of the week, weather conditions and time of day. On a slow day you can allow for greater spacing and maybe do with less staff. At high volume times, space them as close as you are able to handle with the staff on hand. If you are running too fast it may require higher chemical concentrations to get maximum cleaning. If run too slowly, raising dilution ratios may not be able to achieve a good cost per car. Keep in mind, any changes in conveyor speed done after a wash has been set up will require adjustment of the chemical dilutions. Once you have arrived at the speed you can live with set it and don’t change it. Once the speed is set, you can work on balancing your chemicals.

Regardless whether or not you have a gauge to set your conveyor speed I would recommend checking the rate manually. The formula for calculating conveyor speed is


(Time X 2 ) X 60 = Cars Per Hour (CPH)

To arrive at the time portion of the formula time a roller for a distance of 10 feet. Most conveyors are designed with 10 foot sections so you should be able to use the welds on the conveyor as a guide.


The equipment configuration and form of friction used in a friction wash varies a great deal. There are still a few washes using brushes but most washes use some form of cloth or closed cell foam type material or a combination of both as their friction media. Today’s trend is towards the new dense foam material that tends to avoid the potential problem with brushes or cloth of retaining large amounts of water and soil which may damage the vehicle’s surface. Normally a friction wash contains some form of friction on all sides of the vehicle. On the top you may see a mitter curtain, mitters or a top brush. On the sides you may see some form of side brush or high pressure. Many also have wrap around units to clean fronts and backs of vehicles. In today’s tunnel market, there is some form of friction in at least 90% to 95% of washes.

In balancing a standard friction set up there are three basic elements that must be considered – the speed of the conveyor, the type of friction media used and chemical application. As was previous discussed how fast the conveyor is run has a major effect on cleaning as well as chemical application and usage.

In a traditional friction set up there is normally a presoak followed by the application of a shampoo. What products you choose should provide a chemical balance. When choosing your production (cleaning) products balance is a key to removing the various types of soils you are dealing with. Basically there are two different categories of soils: organic and inorganic. In simple terms, organic soils originate from a living source such as vegetation or animal matter. They are best removed with an alkaline or high pH product. Inorganic soils originate from a man made or synthetic, non-living source. For example brake dust, mineral deposits, road salt, clay and abraded asphalt or concrete. They are best removed by acidic or low pH products. Basically low pH products do a better job on glass and chrome and aid in the drying process. The vast majority of the cleaning you will be dealing with will be organic soils so you will tend to use a closer balance between high and low pH products than low in a friction tunnel and more high pH product than low pH in a touch free or hybrid tunnel.

If you use a high pH or alkaline presoak it would be important to use an acidic or low pH shampoo. If you use low pH presoak, a high pH shampoo might be your best choice. If you are using the dense foam material it is also important that the shampoo you select provides good lubricity but not necessarily high foam. Too much foam can cause the media to glide over the foam without making any contact with the vehicle’s surface defeating the purpose of friction cleaning.


In a touch free conveyor car wash the vehicle is washed by a combination of mostly low pressure chemical application and high-pressure water rinses rather than brushes or cloth or foam. Generally the chemical solutions are heated (from 110o to 130o F) before application to enhance their cleaning ability. After the chemical application, high-pressure water (usually 800 to 1200 psi) is applied at an angle (anywhere from 10 o to 45 o) to rinse the chemical and loosened soils from the surface of the vehicle. Angles are used in rinsing to increase impingement or degree of contact with the surface to “peel” or push the chemicals and loosened soils from the surface.

There are two basic methods utilized in touch free washing. Both usually involve two steps. One is the application of a high alkaline product followed by the application of another alkaline and the other is the application of both a high alkaline and low pH product. The two step involving the high and low pH products is the most common one found in tunnels. The rationale for this approach is that the low and high pH products attack a greater range of surface soils than the two step alkaline approach. I have heard arguments as to which product, high or low pH, should be applied first. Some say the high pH should be applied first since it will be neutralized if the application of low pH is used first. Others say the low pH should be applied first to get better cleaning of glass and chrome. My personal preference is the latter but I have seen both methods used effectively. Most operators that employ the two step alkaline do so because of a reluctance to use a low pH product in the wash process. If that is your choice I would recommend increased dwell time, a stronger chemical dilution ratio or a higher solution temperature to compensate for cleaning inorganic soils.

The appropriate selection of the products used is critical in the cleaning process. As mentioned previously a residual high pH may also have an effect on the drying process. High residual alkalinity may also create difficulties for your sealant or protectant. In the other hand, a slightly acidic or neutral surface residual will enhance the drying process. In addition to an awareness of what the residual effects cleaning products may have on drying, the flexibility of choice of cleaning products and the relationship of cost per car can make the difference between cost and performance.


The hybrid car wash blends the best features of friction and touch free washing. In the typical hybrid car wash you will find a limited amount of friction, usually some form of mitter or top brush and possibly a side brush. Also involved in the process will be some form of two step chemical application followed by high pressure. The exception would be the new exterior express tunnels that not only utilize two step chemistry as well as extensive friction. Normally two presoaks are applied followed by a shampoo. Once again most will use both an acidic and alkaline presoak rather than two alkaline applications. In a hybrid, especially with a short conveyor, I would highly recommend that you use a low pH shampoo for better drying results. In today’s market, the hybrid technique is found in most of the washes using some form of friction. It is especially popular in short tunnel (85 feet or less) configurations due to the length of time devoted to the cleaning process


If you are experiencing problems with your drying agent it may not be the product causing the problem. As has been mentioned here previously high residual alkalinity has an adverse effect on drying. Drying is also impeded by any surface soils left on the vehicle after the cleaning process. Of all the products used in the wash process, drying agents are the only ones that have a “window”. In other words, using too much drying agent will negatively affect drying as well as using too little. Most drying agents require anywhere from 1/3 to 2/3’s of an ounce or 10 to 20 milliliters per wash. Check with your chemical rep or product usage recommendations to see what is best for the product you are using.


When selecting your tri-color foam/conditioner and protectant/sealant you should not only consider the “show” and fragrance of those products but the chemistry involved as well. If you are using one of the new “super” sealants the normal alkaline tri-foam/conditioners followed by your protectant and sealant should work well if they are rinsed before the application of the “super” sealant. If you are not using a “super” sealant it is important that you try to balance the surface alkalinity to keep it as close to neutral or acidic as possible to assist the sealant/protectant and your drying agent. In this case, the use of a low pH conditioner should be your choice. Some chemical companies also offer a foaming clear coat protectant in a variety of colors that foam well enough to use in your tri-color application. These types of products also allow for better rising and eliminate any problems created by product run off.


Bug Removal – During certain seasons bug removal can affect the chemical balance in a tunnel wash especially if you are using reclaim in your rinses. Most bug removal products are very high pH. When you use them in your operation you may need to boost any low pH product you are using to balance the chemistry in your wash.

Wheel Cleaning – With the growth in popularity of custom rims and choices many OEMs offer for them wheel cleaning has become one of the more critical areas of car washing. There are many systems out there. One is the single foamer or double foamer using either a two step alkaline or one step acidic and one step alkaline. Some use a K nozzle setup while others simply use the treadle with a regular nozzle to apply the wheel cleaning product. The three main factors aside from the chemical or chemicals of choice are dwell time, surface contact and high pressure rinse. The more dwell time the better and of course, the better surface contact or coverage the more complete the cleaning is. An effective high pressure rinse is also essential for on line wheel cleaning. The more pressure and impingement provided the better the result. Your selection of wheel cleaning products should always be taken into consideration as part of the chemistry of your wash.

Prepping – Although it is desirable to eliminate prepping from a time and cost perspective, very few operations can avoid some form of manual prepping of the vehicle. In too many cases, the real washing is done there. The best way to reduce or even eliminate prep time is to do the best job possible in tuning or balancing the tunnel. Almost all products used in prepping are alkaline and in some cases with a pH over 11. If you are doing manual prepping, try to use a product that is only slightly alkaline rather than the higher pH types. This is especially important if you are using a two step low/high presoak format. A high alkaline prepping product could affect the cleaning ability of your low pH presoak if it the first application on line.


As you can tell by now, balancing a tunnel taking into the considerations all of these cleaning factors is no easy task. Hopefully this article will increase your awareness of the importance of balancing the chemistry in your tunnel. If you are lucky enough to have a well trained chemical rep some of this work may be have already been done for you. The true professional rep develops a “feel” for the cleaning process and often can make a positive effect on cleaning by making the proper adjustment on the factors most involved in the cleaning process in their customer’s tunnel.

It is often difficult to pinpoint the exact problem and solution for that problem. Sometimes it may be increasing the water temperature. Other times a low pH shampoo will increase cleaning and enhance the drying process. Still others increasing the dwell time of a particular chemical or increasing the dilution may make the difference. There are many variables in the process that work together. The real trick is to isolate the problem and solve it rather than making wholesale changes. Each tunnel has its unique “quirks” that need to be dealt with on an individual basis. As an operator there is no substitute for gaining an understanding and experience with what works best in your tunnel.

Updated Bio

Ron Holub has been in the car wash industry for almost 30 years working for several national carwash chemical companies, owning a car wash and detail supply company, and serving as a general manager for a national car wash chain. He currently works for Townco Washing Systems in the Atlanta area and can be reached at [email protected].