Water is a major expense when considering your cost of goods for a car wash operation. Detergents, waxes, electricity, and gas (for heating and hot water) all fit into the cost of goods category. These expenses are directly related to your car wash volume.

Car wash equipment uses water to help rinse the dirt and grit off of the friction material of the wraps, mitters, top brush, rockers, and van high-side washers. It is important that this material is rinsed before its rotation touches the vehicle surface.

Chemicals are applied to the vehicle’s surface to help break down the dirt and road film. The cloth material agitates the dirt off of the vehicle’s surface. The spray of water on the cloth material rinses the dirt particles off the cloth for the next rotation or movement.

The goal is to deliver a clean, dry, shiny, and spot-free vehicle to the customer. This can be achieved by providing spot-free water as the final water touching the vehicle’s surface.

Water does not cause spots. The dissolved solids that water absorbs is what causes the typical water spot. Water evaporates and leaves these dissolved solids behind. When looking at the total dissolved solids (TDS) levels, start at the exit end of the car wash, and flow towards the entrance of the wash. You can use water with higher TDS levels as the vehicle enters the tunnel. Our objective is to use the high TDS water at the start of the wash and have low TDS water at the end.


Most car washes use reverse osmosis (RO) water as the spot-free final rinse, which is low in TDS. It’s not necessary to dump gallons of RO water on a vehicle’s surface to get the final spot-free rinse, you only need to displace the city water. The gap between the final rinse water and the spot-free rinse is called drip space. Allow 2 to 4 feet of drip space before you apply the RO rinse. The greater the drip space, the less RO water will be required to displace the water on the vehicle’s surface.

If you can’t increase your drip space, you can opt to install a flash blower. A flash blower is a single blower located in the wax and rinse area of the tunnel. Aiming the flash blower towards the windshield area will blow out any standing water in the cowl area and the top of the vehicle and will knock down the excess water on the vehicle’s surface. With less water on the vehicle, you will use less spot-free water as your final rinse.

In order to be efficient with the RO water usage, you need to be able to adjust the pump pressure that is applying the spot-free rinse. The higher the pump pressure, the more water will pass through the nozzle. If you have the ability to adjust this pressure, you can reduce your water usage. If you are using a ball-valve to control the flow of the spot-free water, this can create pump problems as it is putting extra pressure on the pump seal. The spot-free re-pressure pump is a positive displacement pump; it wants to discharge all of the water it is pumping. By closing the ball-valve on the pump discharge, the full flow of the pump cannot get out of the pump. The pump will then generate heat which may cause damage to the pump seal and the impeller. To prevent this from happening, a pressure relief valve can be installed on the pump discharge. The pressure relief valve will discharge the excess spot-free water out of the pump and back to the spot-free storage tank. By doing this, you can reduce your spot-free water usage and still deliver an excellent-quality vehicle.

RO units actually give you two different water sources. The RO (spot-free) and the concentrate stream (RO reject). The TDS that was in the spot-free water is now collected in the concentrate stream (it is a concentration of the TDS).

Most RO units are fed with a soft water supply. This means that the concentrate water is a clean, soft water source.

Typically, soft water feeds your soaps and foaming lubricants where the cloth material touches the vehicle’s surface. Concentrate water is high in TDS. When you add soaps to your clean city soft water, it raises the TDS level in the water. When using the concentrate water here and soap is injected, the higher TDS concentrate water works great. You and your customers will not notice this change.


Reclaim water is typically higher in TDS than your fresh water supply. Using reclaim water in the wash section allows you to save water. It is okay to see color in reclaim water, but it should not look dark, dirty, or oily, or have an odor.

High-Pressure pumps are one of the biggest water users in the tunnel. Each high-pressure pump can use 20 to 25 gallons per minute (GPM) or more.

This is one of the best applications for the use of reclaim water. Reclaim water can be high in TDS and is perfect to use in the front and middle of your car wash tunnel. From this point towards the exit, we need to start reducing the TDS levels in the water being applied on the vehicles surface.

After the high-pressure application, a mitter or top brush works well to knock off excess water. By reducing the amount of water sitting on the vehicle’s surface you can use less fresh water for your sealants and waxes.

I recommend using a hard water source, not RO concentrate, for the waxing area as hard water has calcium and magnesium. These particles help neutralize soap, soap suds, and foam. When you use hard water with wax products, they knock down the chemical carryover of the cleaning products.


After the wax, clear-coat, and drying-agent applications are completed, you should rinse the vehicle’s surface with a final, clean, hard water rinse. Hard water helps to rinse off any residual chemistry that is not attaching to the vehicle’s surface. The water on the surface of the vehicle should only be city hard water.

If you are using the RO concentrate water in the waxing area, you are using high TDS water and will require more RO water for final rinsing to displace the high TDS water. Again, the concentrate water is typically soft water. Soft water does not neutralize soaps, it actually can re-active the soap causing spots on an exiting vehicle.

RO water typically has zero TDS which means that it is only H2O. Water likes to dissolve particles into itself. This is why it is called total dissolved solids.

When RO water touches the water that is on the vehicle’s surface, it instantly starts absorbing the TDS that is in the hard water, this is okay. Our goal TDS that is left on the vehicle’s surface is 50 PPM or less. If there is any soap on the vehicle’s surface, the RO water will adsorb it and typically the TDS level will go above the 50 PPM. If this occurs, you will start noticing spots on the vehicle’s surface. It’s not that the RO water isn’t working, it’s that the vehicle was not rinsed well enough prior to the spot-free water being applied.


The best way to apply your spot-free water is a rain bar. Rain bars have streams of water coming straight down. The ports or holes in the rain bar give you an excellent stream of water which is much stronger than a standard arch with 13 V JET nozzles. V JET nozzles deliver a spray pattern that, when the blowers turn on, can actually keep the spot-free water from touching the vehicle’s surface. When applying your spot-free rinse, keep this in mind: gravity always wins. Spot-free water will travel down the sides, hood, and trunk of the vehicles. If you use V JET nozzles to apply your spot-free rinse, spray the complete vehicle with more than one size of nozzle; larger nozzles should be used on the top, smaller nozzles on the side, and the smallest nozzles should be used on the rocker panel areas of the vehicle. As the water runs down the side of the vehicle, the spray patterns from the lower V JET nozzles will help slow the water running down the vehicle’s side and give you a better rinse. This nozzle arrangement will help you save RO water and still produce the exit-quality vehicle you and your customers are looking for.

Bryant Ruder is the president of Eureka, IL-based SoBrite Technologies.

Visit the company on the web at www.sobrite.com. You can contact Bryant at (309) 467-2335 or via e-mail at bryant.ruder@sobrite.com.


TDS – Total Dissolved Solids

TSS – Total Suspended Solids

ppm – Parts Per Million

mg/L – Milligrams Per Liter (ppm and mg/L are two different scales, but equal the same values)

Water Hardness – The amount of dissolved calcium and magnesium in water

Soft Water – Water free of calcium and magnesium. This is achieved by a water softener where the hardness ions are exchanged with sodium ions.

Spot-Free Water – Water that has ions removed, low TDS

Permeate Water – Product (Spot-Free) water produced by Reverse Osmosis process

Concentrate Water – Discharge stream of water produced by Reverse Osmosis process

Ion Removal Process – There are three ways to remove ions from water:
• Distillation
• Deionization
• Reverse Osmosis