Types of Water in the Car Wash

Types of Water in the Car Wash

Posted by: Paul Spence on May 6, 2021 7:00:00 AM

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

 Fresh water

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


Soft water

Soft water is water that is less than 20 mg/l (1 grain = 17.1 ppm). Most of the hardness in the water comes from the Calcium, Magnesium, and Iron. A 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.


Reclaim water

Reclaim water is recycled water that has been used during the car wash process. The water flows through various settling tanks to drop out or separate the solids in most standard systems. From there the water is pumped through the reclaim system which cleans the water to deliver to the wash and recirculates the water to prevent stagnant water. 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 very typical. For rollover or automatic car washes, usually the reclaim water is applied on high pressure wash passes or used to lubricate brushes. Both tunnel and rollovers 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.


Spot-free water or Reverse Osmosis water (RO)

What is it? – Spot-free or RO water is water that has gone through an RO system or Deionization tanks. This process will filter or strip the TDS from the water. Water that is less than 25 PPM (Parts Per Million) or TDS (Total Dissolved Solids) is Spot Free water.

Where to use it? – 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.


RO Rejected water

What is it? - 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 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% higher. For instance, if your Fresh water coming into the RO is 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 TDS (PPM) in the water. Therefore, you do not want to use RO Reject water to mix with your chemistry (soaps, waxes, etc.).

Where to use it? – Reject water is very good a breaking up foam. The best place for you 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.

These are the types of water used in a car wash. Stay tuned for another post outlining the best and most efficient ways of utilizing this water while saving your business money.

Topics: PurClean, Water Conservation, Technical
Paul Spence

Paul Spence


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