Can You Wash Your Car With Hard Water? (Answered)

Written by

Bruce Sonnier


Marcus Dutton

can you wash your car with hard water

Hard water causes issues in cleaning, plumbing, hygiene, and the smell and taste of drinks. For car owners in areas with hard water, “Can you wash your car with hard water?” would be a concern. This article would answer that.

Unfortunately, hard water has negative effects on vehicle washing, so it’s not advisable to use it on your car. However, with some remedies that help prevent these issues, you can wash your car with hard well water or tap water.

Can You Wash Your Car With Hard Water


Yes, washing car with hard water is possible, but it’s best not to do so to prevent its negative effects.

Thankfully, if you’re the type to do it yourself at home, you’ll still be able to wash your car with the help of some remedies, which we’ll discuss later on.

Definition and Characteristics of Hard Water

Hard water means the water has a high concentration of minerals. The most common minerals in hard water are calcium and magnesium. Sometimes, they may also contain iron and manganese.

The most common sources of those minerals are dissolved limestone, magnesium sulfate, and calcium carbonate.

In determining the hardness of water, people often use a measurement called grains per gallon (GPG), with 3.5 GPG and higher signifying hard water. You can check if you have hard water by using a digital tester or hardness kit.


Or you can do this simple test of filling about 1/3 of an empty, clear water bottle with water, adding a drop of dish soap, and thoroughly shaking the bottle. If you did not end up with many fluffy bubbles but milky-looking water, then your water is hard. Or you can ask a water hardness expert to check your utility supply.

Potential Negative Effects of Washing a Car With Hard Water


  • Water Spots or Streaks

When car washing, water tends to dry on the car exterior, especially when it’s hot. And when hard water is used for washing a car, as it evaporates, water spots and streaks can form on the surface because of the high mineral content.

When you get them in your car, you’d have to go through the trouble of removing mineral deposits. If you don’t remove them from car surfaces immediately, they can dull the paintwork, etch both the paintwork and glass, and corrode the metal parts.

  • Hinders the Suds or Foam Generation

The minerals in hard water bind to car wash soap’s molecules, and as a result, the soap can’t fully dissolve, and you wouldn’t be getting much suds or foam from it.

Instead, you’d end up with soap scum, which isn’t so efficient to work with. And you’d have to increase the amount of soap to make more suds or foam, which would be more consuming and costly.

  • Clogs Pipes, Plumbing Fixtures, and Appliances

The minerals in hard water can accumulate in pipes, plumbing fixtures, and appliances. They would form scale build-up and eventually cause clogs.

Remedies for Washing With Hard Water

1. Work away from the hot sun


It’s best to wash your car during times that aren’t very hot, like mornings or evenings, to prevent water spots and streaks. Avoid washing under the sun’s hot temperatures.

2. Quickly and thoroughly dry the car exterior


Wiping dry your car’s exterior parts quickly and thoroughly will help prevent the water from evaporating and leaving spots and streaks. It would also help to wash and dry your car section by section, meaning after washing one section, immediately dry it too.

3. Coat your car with wax or sealant


Wax and sealant can help minimize water spots and streaks or even prevent them entirely with the hydrophobic protective layer they provide. Their hydrophobicity makes water roll off, which results in few to no spots or streaks. And if they do appear, they would be easier to remove because they are merely on the protective layer.

4. Use a mineral deposit remover or vinegar and water


Apply a mineral deposit remover on the car after washing it. Use soft cloths to buff the imperfections away until you get a spotless finish.

As an alternative, combine vinegar and water in a 1:3 ratio, then spray it on the car before washing away all residues.

5. Polish the vehicle


Car polishes can remove water spots as well as swirls and light scratches, making them an excellent solution for washing cars with hard water. Use these as the final step in your cleaning routine.

6. Rub car with clay bars


Clay bars can remove tree sap, oxidation, and water spots to make vehicles look smoother. You only need to wet and rub them on mirrors, car paint, etc.

Alternatives to Washing Your Car With Hard Water

1. Cleaning solution designed for washing with hard water


There are car wash soaps and shampoos designed with a special formula for washing vehicles with hard water.

Some good examples are Meguiar’s NXT Generation Car Wash, Xtreme Solutions Xtreme Suds Car Wash, and McKee’s 37 SiO2 Auto Wash, which can soften hard water to wash car and prevent unsightly stains.

2. Water softener


In a water softening system, hard water is passed through resin beads that exchange the mineral ions with sodium ions, which results in soft water for car washing. It’s worth noting that this requires salt and regular salt refills to function.

3. Reverse osmosis system


A reverse osmosis system is a method of treating water that doesn’t only eliminate the minerals but also other impurities. This would be a good option if you want something more powerful that can provide more pure water, not just for your car but also for the health of you and your family.

It filters out the minerals and other impurities by forcing water toward a semipermeable membrane. The filtered particles are then flushed out, resulting in purified water.


There’s no need to worry about “Can you wash your car with hard water?” anymore, now that you’ve been educated about it in this article.

Although the answer is yes, keep in mind that it isn’t necessarily good to go this route because of its negative effects. But with some hard water car washing remedies, you can safely clean your vehicles and give it that showroom shine.

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