Let us start by talking about water and knowing where to use it in the car wash process. As we all know, the price of water and sewer services rise year after year. Figuring out where to use the different types of water in your wash is important.


There are many different types of water available for use in your car wash. I will discuss the various water types and when or where they should be used.

1. Fresh Water

What is it? Seems simple, but fresh water, although clean, can be from different sources and thus of varying quality. Fresh water can be from the local municipality or possibly from a well system. With either water source, testing your water is necessary. Items such as TDS (total dissolved solids), hardness, or iron content, for example, can make a big impact on the wash quality. Testing will help determine if the water source at your site will need pre-treatment before it is used in the wash process.

2. Soft Water

Soft water is water that contains less than 20 mg/l of CaCO3 or 4 grains per gallon (1 grain = 17.1 ppm). Most of the hardness in the water comes from calcium, magnesium, and iron. A water softener will pull the calcium and the magnesium out of the water and replace it with sodium by a process called ionic exchange. Soft water can be used in multiple locations of the wash but is most commonly used to mix with your chemicals and to feed the reverse osmosis (RO) system.

3. Reclaim Water

Reclaim water is recycled water that has been used during the car wash process. In most standard systems, the water flows through various settling tanks to drop out or separate the solids. From there the water is pumped through the reclaim system which cleans the water and delivers it to the wash. It also recirculates the water to prevent the water from becoming stagnant. Most systems will clean the water to a level between 5 to 70 microns, depending on the system.

Reclaim water can be used in many areas of the car wash. For tunnel systems, the front half of the car wash up to the mitter curtain or the last top-brush before the wax arches is typical. For in-bay automatic car washes, the reclaim water is usually applied on high pressure wash passes or used to lubricate brushes.

Both tunnel and IBAs can also utilize undercarriage applications which helps improve the overall reclaim water percentage saved.

Always make sure the reclaim water is rinsed off before the first wax arch. If you do not rinse off the reclaim water before the wax is applied, the wax will seal the reclaim water to the vehicle.

4. Spot-Free Water or RO Water

Spot-free or RO water is water that has gone through an RO system or deionization tanks. This process will filter out or strip the TDS from the water. Water that contains less than 25 ppm of TDS is spot-free water.

Spot-free water can be used on the last arch or last pass of the wash process. You can also use RO water to mix with your chemistry. Some sites will use the RO water to rinse the tunnel windows.

5. RO Reject Water

Reject water is water that has been discarded from the RO system. Reject water has been run through a carbon tank to remove the chlorine, then through the 5-micron prefilter to remove the large particles from the water. It is then pushed through the reverse osmosis membrane and the water is separated into spot-free water and reject water. The reject water or concentrate is then discarded. This water is higher in TDS than the city water, roughly 80 percent higher. For instance, if your fresh water coming into the RO is at 200 ppm, the concentrated reject water coming out of the RO will be around 350-400 ppm. RO reject water is very good at breaking down foams and rinsing. The reason for this is the high level of TDS in the water. Therefore, you do not want to use RO reject water to mix with your chemistry (soaps, waxes, etc.).

The best place to use reject water is before the first wax arch. The reject water will rinse the reclaim water off the vehicle before it is sealed in by the waxes. Reject water is hard and it will break down the foam on the car before the waxes.


The first thing to utilize in the quest to save water is a reclamation system.

Reject Recovery Water

If the amount of reject water in the reject storage tank does not go up and down throughout the day, you are not using enough of the reject recovery water. The optimal situation will be if the storage tank is empty by the end of the day. That means you are using all the reject water that the RO system is discarding.

Note: RO systems will waste water to make water. It is important to find an RO system that uses less water and is most efficient.the goal is to be efficient and good stewards of the environment

Reducing the Waterflow to the Rinse Arch

Rinse arches flow at different gallons per minute (GPM), depending on the arch and the manufacturer. To save water you can reduce the flow to the rinse arch by adding either a ball or gate valve to the incoming line. Then you can close the valve 10 percent, for example, which would restrict the flow of water to the arch, reducing the arch output.

You can also replace the tips in the spray arch. If you have an arch with 10 0.7 GPM tips in it, the flow will be 7.42 GPM at 45 PSI. If you reduce the tip size to a 0.5 GPM tip, it will reduce the flow to 5.30 GPM at the same pressure of 45 PSI. With the vehicle under the arch for 20 seconds this will save 0.69 gallons per vehicle. At 1,000 cars per day, this will save 690 gallons per day.

Using a Low-Pressure and Low-Volume Pass

In-bay automatic car washes: A high-pressure reclaim-water pass followed by a low-pressure freshwater pass will use less water and still rinse off the soap or conditioners and have the vehicle ready to receive waxes and drying agents.

Tunnel car washes: High pressure pumps can have their pressure reduced with the unloader. The extra water will be fed back to the inlet of the pump. By dropping the pressure, it will drop the GPM of the pump. A 10 percent drop in pressure can save a couple gallons of water per vehicle.

Spot-Free Water Savings

When using the “mirror rinse”: Do not use the spot-free arch and the mirror rinse on the same activation signal, instead have each application act on its own signal from the controller. This will allow the mirror rinse to be turned on at the vehicle’s mirrors and at the back of the vehicle only. The vehicle will be under the spot-free arch for 20 to 25 seconds and the mirror rinse will use 8 GPM. If you remove 10 seconds from the mirror rinse it will save you 1.1 gallons per vehicle.

Setting Up the Wash and Wash Passes to Use Less Water

Using the correct timing in the car wash is key. Make sure the applications turn on and off at the front and back of the vehicle. If the timing is not correct during the course of the wash, it will waste water and chemicals. Let’s use the wax arch or wax pass on your system, as an example: If the arch turns on 1 second before the front of the vehicle and then turns off 2 second after the back of the vehicle has passed, this is a total of 3 seconds more than needed. Three seconds will add up fast. Let us say that you wash 1,000 cars per day so that wax arch is going to unnecessarily use 3,000 seconds of wax and water. That is 50 minutes of water and wax that is not going on the vehicle and is being wasted. The wax arch will use 10 GPM of soft or city water. So, if the arch runs for 50 minutes, that is 500 gallons of water that is wasted and that is 1,900 ml or 64.24 fluid ounces of wax or soap that is also wasted for those 1,000 cars.

Using Reclaim Water for Other Purposes Around Your Car Wash

You can use your reclaim water to irrigate the landscaping around your car wash. Please check to see if your local municipality allows this. It is easy to set up a signal from the sprinkler-timer to the reclaim system. The signal will make the reclaim system ramp up, giving you 40 PSI of water pressure to the sprinkler system. The water coming out of the reclaim tank will be high in TDS. The county often allows a certain amount of reclaim water to be used, usually per square foot of grass or plants. If you cannot use reclaim water for your irrigation system, you can try using reject recovery water on your landscaping. It is higher in TDS than the city water, which is good for the plants.


We have discussed the various types of water that is and can be used in the car wash. We talked about how to be most efficient with the timing and how we use the water. We discussed some of the ways to save water. The goal is always to be efficient in order to save money, but also to be good stewards of the environment by using the water wisely. Water and sewer price are rising every year. Make every drop count.

Paul Spence is technical sales manager for PurClean. You can visit the company on the web at www.purclean.com.