Does Soft Water Leave Water Spots On Car (And How To Make Water Spot Free)

Washing a car sounds like a good idea to eliminate the accumulated dirt, dust, insect remains, bird droppings, and grime on the surface.

But then, some spots could stay behind after washing and drying the car, which most people find annoying and unpleasant.

They are due to using hard water to clean the vehicle.

Hence, people wonder if soft water is a good alternative to avoid unsightly marks.

Using soft water to clean cars can also leave water spots on the car’s surface, but they are much easier to wipe off than hard water spots. Softening water doesn’t eliminate minerals from the water. Rather it exchanges calcium and magnesium, the hardness minerals, for sodium, whose deposits are easier to clean.

Are you curious how soft water doesn’t guarantee a water spots-free car washing experience?

This article explains more in detail; read to the end to understand more!

Does Soft Water Leave Water Spots on Cars?

According to research, using soft water has many benefits, including preventing hard water damage on appliances and promoting the strength of detergents when washing.

Hard water has minerals like magnesium and calcium that react with water to form scum, reducing the efficiency of car-washing soap.

Therefore, soft water seems viable to make car washing easier, including reducing the appearance of spots after washing.

Soft water has more sodium and less calcium; therefore, it still contains minerals that remain on the car’s surface after the water has evaporated. These are the spots normally seen on the car after washing. However, marks from soft water are easier to clean off because the minerals present don’t form the scaling that usually results from hard water.

Softened water is the best for washing cars, especially if it is low in TDS (Total Dissolved Solids).

TDS is the total mineral content in water, representing a fraction of what makes water hard.

Wet Car Mirror from Car Wash

The Interconnection Between TDS and Spotting

The potential of water to leave spots on cars’ surfaces can be predicted from the TDS.

The mineral content influences waters’ spotting potential, so the higher the TDS, the more likely it is to experience spotting.

Therefore, eliminating the minerals could be the solution to avoiding spot formation after washing the car.

However, it is practically impossible to strip the water of all the minerals in most cases.

Most of the processes of softening water by removing all minerals are very expensive for the average home user, unlike commercial car washing establishments.

Also, it should be noted that both soft and hard water have essentially the same TDS, but why so?

Why TDS Remains the Same for Hard and Soft Water

As indicated above, TDS is the predictor for spotting. Thus, it shouldn’t be confused with water hardness, as both are parameters for testing water quality.

Water hardness results from carbonate, chloride, and sulfate salts in calcium and magnesium.

On the other hand, TDS is the indicator of organic and inorganic substances in water that can’t be filtered with filter paper.

Soft and hard water have the same TDS because softening doesn’t eliminate minerals from the water. It only exchanges calcium and magnesium (which cause water hardening) for sodium in almost equal proportions. Thus, softened water has more sodium and less hardening minerals, but the TDS remains more or less the same.

Therefore, it doesn’t matter whether the water is hard or soft.

Spots will remain on the car after washing because of the TDS.

Sodium ions in the softened water are less potent; hence the water spots are easier to clean from the vehicle than hard water spots.

How Can I Make My Water Spot Free?

Softening water is the best way to make water spot-free after washing cars. There are several tips individuals can utilize to soften water, including the following:

  • Reverse osmosis
  • Boiling hard water
  • Using a cleaning solution
  • Softening using distilled white vinegar
  • Using baking soda

These tips are explained below:

Use a Reverse Osmosis System

A Reverse Osmosis (RO) system lowers the TDS of water, making it ideal for car washing because the spots don’t remain on the vehicle after washing and drying.

Some individuals use water softeners to exchange the water hardening minerals for sodium, and then the RO system removes added salts from the water, reducing TDS.

Boil the Water

Boiling water precipitates dissolved calcium bicarbonate from temporary hard water.

The calcium component is eliminated from the water, softening it and making it spot-free after washing the car.

Use a Cleaning Solution

Using a cleaning solution intended for hard water neutralizes the hardening minerals.

Therefore, the product alleviates hard water effects, including leaving spots on cars after washing.

Use Distilled White Vinegar to Soften

White distilled vinegar is very acidic; hence, it helps neutralize the calcium (which is alkaline) in hard water, softening it.

Therefore, adding vinegar to hard water is one of the methods to make water spot-free.

Add Baking Soda

Baking soda softens both temporary and permanent hard water because it contains sodium carbonate, which removes the hardening minerals (calcium and magnesium) from the water.

Hence, adding it to water for washing cars makes it spot-free.

After making the water spot-free, individuals can also utilize the right washing techniques to prevent water stains on their vehicles. The following is a process that helps prevent water spots after washing:

  1. Spray the softened water on the car.
  2. Use a wet microfiber towel or cloth to scrub car shampoo on the car’s surface, one section at a time.
  3. Rinse the washed part immediately after scrubbing it before moving to the next surface until the whole car has been cleaned.
  4. Dry the vehicle with a microfiber cloth or towel.

Key Takeaways

  • Soft water can also leave water spots on a car, but it is much easier to wipe off than hard water spots.
  • TDS (Total Dissolved Solids) is the total mineral content in water, and it predicts the potential of water to leave streaks on a car after washing.
  • The TDS in water remains the same even after softening.
  • Reverse osmosis, boiling hard water, using a cleaning solution, softening using distilled white vinegar, and using baking soda are tips to make water spot free to clean cars.


Jan-Lucas Ganssauge
Jan-Lucas Ganssauge