Professional Carwashing & Detailing

Good clean water

October 11, 2010

Let’s start with the basics. There are five factors to cleaning a vehicle and they are all of equal importance:

  • Water quality;
  • Mechanical action;
  • Chemistry;
  • Time; and
  • Temperature.
This article will focus on improving water quality at your express exterior carwash for better washing results. This starts with understanding the water your carwash is currently using.

Most water authorities have embraced the digital age, so head to the computer to check your provider out on the Internet. Organizations providing water must submit a water quality report every four years and these are usually posted online or available by phoning your utility and asking for a copy.

As a second method of checking water quality, most carwash distributors have the necessary equipment to test water. Finally, if you adhere to the “It’s not done right until you do it yourself” business advice, you can purchase testing equipment and learn to perform these tests whenever the mood strikes.

Go for the tap water

Tap water, either from a municipal water supply or private well, ranges in quality from great to terrible. Some symptoms of poor quality tap water are:

  • High TDS (total dissolved solids);
  • Too high pH;
  • Too low pH (7.0 to 7.4 would be neutral and the ideal);
  • Turbidity, cloudy appearance;
  • Iron presence; and
  • Hardness.

All of these diagnoses should be on your water quality report. If you’re drawing from a private well, simple tests (TDS, hardness, chlorine) conducted at the site by your carwash equipment representative will help with determining the quality of the fresh water.

Using reclaim water

Reclaim water is water that has been used in the wash process, then cleaned and reused. Many municipalities now require some form of reclamation or recycling system prior to permitting and having one may assist in avoiding expensive impact fees. For wash quality it is always better to have some fresh water in every cycle. Water reclamation systems are not new in vehicle washing and there are several different technologies in current use.

No one wants to live near a sewer plant, the water is foul and if the wind is blowing in, the odors will force you to your knees, but for water to be reused certain steps have to be taken to clean it up.

The first major treatment in wastewater is sedimentation which is the removal of a substantial amount of suspended matter. This is done in settling ponds in a municipal system where water can set for days or even weeks and allow the solids that are heavier than water to sink to the bottom.

In a carwash system the settling tanks are usually underground. If your incoming stream of water contains lighter than water material — like floating trash or hydro–carbon based oils — these products will float on the surface of the settling pond. In a carwash, the total amount of water kept in the system is considerably less than what is kept in the sewage system of a city and naturally will have less time to settle before it is called on to be used again.

All reclamation or recycling systems use a tank system to capture the water after it is used. These are often called clarifier tanks or oil–water separator tanks. The suspended solids are allowed to settle in these tanks, thereby clarifying the water. If the tank system is properly sized not only will the solids settle to the bottom, the oils and lighter than water contaminants will rise to the top and become trapped out of the reuse stream.

Batch or on demand?

After the tanking system, reclamation recycle systems split into two types, the first we will call a batch system.

A batch system draws water from the end of the settling tanks and processes the water to systems that are essentially micro sewage treatment plants that treat the water with multiple filtering elements and or media and store the water in additional tank(s) for future use in the wash process. These are typically the more complex systems and usually require multiple pumps.

Batch systems require proper sizing so as to have enough time for the processing of the water to be accomplished before the wash demand calls for the clean water, if the system is undersized you will be using water that is not as clean as it should be to make up the deficit.

The second type of system we will call on demand. With the same clarifier settling tank system, the on demand system processes the water to the acceptable level of solids with some or all of the following:

  • Cyclonic separation;
  • Backwashing filters;
  • Media tanks; and/or
  • Disposable filters.

This is accomplished as the wash demands water; it does not require the additional holding tanks.

At the very minimum a reclaim system must remove the larger suspended materials. The better on demand systems will also have the recycling capability to maintain odor control. In most cases this requires a separate pump. Remember that this usually increases the size of the equipment and the price as well.

Once the water is processed and stored it can go septic very quickly causing unpleasant odors when it is used. Unless it is being treated on an ongoing basis, this is usually accomplished by a recirculation pump with some form of a biological, chemical or ozone injection.

Know about RO

Spot–free water is water that either naturally or through processing has a TDS count below 20 parts per million (ppm). The overwhelming majority of spot–free systems in current use are reverse osmosis (RO) systems. RO systems do have an impact on water conservation and at most will require two gallons of fresh or tap water to make one gallon of product.

All RO systems work much the same way: Tap water is introduced into a pump which increases the pressure to 180 to 250 psi and is forced through a membrane or membranes. The most common membrane size used in carwash applications is 4x40 inch and this membrane requires five gallons across the surface of the membrane for every gallon of permeate (or product) water you make.

The RO system will deliver a final spot–free rinse to the vehicle at the conclusion of the wash process or as it exits the wash. The effective use of spot–free water will displace all residual chemical and mineral laden water (including reclaim water) and allow the entire vehicle including glass, chrome and painted surfaces to dry perfectly spot–free.

Most RO manufacturers re–circulate a portion of “bad” or concentrate water back into the inlet stream. The standard seems to be out of the five gallons you started with, you will yield:

  • One gallon made;
  • One to drain; and
  • Three gallons re–circulated.
  • Pre–treat the tap

It is recommended to pre–treat tap water before it goes into the RO system. Some water conditions will require additional pre–treatment, so consult the equipment supplier. Because most municipal water systems use chlorine as an anti–bacteria treatment and membranes do not tolerate chlorine, it is necessary to remove the chlorine before the RO.

A simple, activated charcoal filter tank works for this purpose and most RO manufacturers include this as part of the system. All systems will have some form of a pre–filter — usually a 5 micron pre–filter — that is provided to separate the larger solid material from the water. The RO membrane will have an easier time separating dissolved solids from the water if the large particles are removed by the disposable filter first.

An RO system filter needs to be changed at least on a monthly basis; some water conditions may require more frequent changes. When filters are not changed regularly RO systems may exhibit some or all of the following symptoms,

  • Poor quality of product water;
  • Significantly lower production rate;
  • Damage to the RO pump; and/or
  • Plugged RO membrane(s).

RO systems are typically sold by the amount of water they produce in a 24–hour period. This is usually at optimum performance with 77° F feed water. If your calculations are on the close side, upsize your storage tank or select the next unit size up.

As you can see, understanding your reclamation and RO systems can help you to better diagnosis problems and improve water quality. Happy washing!


Charles Borchard is the VP of Operations for New Wave Industries, the manufacturer of PurClean Spot–free Rinse Systems and PurWater Water Recovery Systems and is in his nineteenth year in the water treatment business. He can be reached via email: cborchard@purclean. com if you have questions about this article.