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How To Safely Wash a Car with Hard Water

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Man pressure washing car

Let us guess — you just got finished painstakingly cleaning your car only to find white spots all over it. Almost like Casper rubbed his chalky fingers all over your ride. Before you call the Ghostbusters, let’s see if I help explain. These spots are probably the result of using hard water on your ride.

If you want to know how to successfully wash your car with hard water, stay tuned. I’ll be reviewing why hard water sucks, why it should be avoided, what you can do about it, how to remove these water spots, and how to prevent them in the future.

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What Is Hard Water

What is hard water? No, it’s not solid water that hurts when it hits you. I’m pretty sure that’s called ice. Hard water is just a term that means the water itself has a lot of minerals in it.

Things like sulfates, calcium, and magnesium play into how hard or soft the water is. It’s not a car term, it’s a water term.

Why Does Hard Water Matter to a Car?

Okay, so why am I talking about hard water if it has nothing to do with cars? Well, it really matters when you’re talking about washing a car.

When most people wash their own car, they’ll use a garden hose, soap, and some towels. The garden hose is pulling water right from the same source that your home is.

This is exactly why you should care about hard water. It can cause a special phenomenon when washing your car called “water spots.”

Man washing car with water gun

The Truth Behind Hard Water Spots

These water spots can be the source of a massive headache after you wash your car. Spending the time to perfectly wash your car will be in vain if you’re dealing with hard water. In the end, you’ll be left with massive, chalky-white spots all over your car.

These are buildups of those minerals that make water hard in the first place. The water from your hose will deposit the minerals all over your car, the minerals will bunch up, then when you dry you’re left with water spots.

You’ll notice that simply wiping them with a paper towel afterward won’t do much. Heck, you can even rub your finger over the water spot and might not see any improvement. 

Testing for Hard Water

Not sure if you have hard water at your house? I won’t run through the whole test procedure, but just know that there are special kits you can get to test for hardness. You can also call out a water hardness expert and let them take a look.

If you want a quick and easy answer, grab an empty water bottle. Fill it up a third of the way and drop in a little dish soap. Cap it, shake the bottle hard, and take a look inside.

If you have a lack of fluffy bubbles and the water looks milky, you have hard water. Equally, you can run the hose on your car, let it dry, and check for water spots.

hand holding a spray bottle

Areas with Especially Hard Water

Some metropolitan areas have especially hard water. If you live in Las Vegas, Jacksonville, Tampa, or San Antonio, you can assume your water is hard.

That’s not a problem because I’m about to teach you how to wash a car with hard water.

How to Wash a Car with Hard Water

After establishing that you have hard water, you need to learn how to appropriately wash your car. Don’t worry, I’ve got you covered. Here are some of the tips that I’ve personally used over the years. See which one works for you.

Try Some White Vinegar

It seems like every DIY list in the history of DIY lists has white vinegar on it. I’m not going to break that tradition today. White vinegar is the unsung hero of the kitchen. It is slightly acidic which is great because it eats up the mineral deposits on your car.

Acidity is key in the cleaning of water spots. It’s why there are so many citrus-based cleaners on the market.

At any rate, fill up a spray bottle with a 3:1 ratio of water to white vinegar. Try it out on a tiny portion of your car before doing the whole thing. This is a way to test your mixture without potentially ruining the top coat of your car.

Apply ONR Wash & Shine

Want a more professional option? Try Optimum No-Rinse (ONR) solution. This is a wash-and-shine product that replaces soap and allows you to wash your car without a hose. Here’s how it works:

Start with a mixture of 2 cups of ONR and 2 gallons of water. Put your towels in the mixture and let them soak. Grab an empty spray bottle and fill it up with the mixture.

Use the spray bottle and soaked towels to apply a light coat of the mixture to your car, starting from the top and working your way down. When you’re done, wipe it away with a dry microfiber towel. You should notice a light coat of ONR that’s left on your car.

As the name suggests, you don’t have to rinse after you’re done. That’s the beauty of this product — no need to worry about hard water.

Optimum No Rinse Wash & Shine – 32 oz. – NR2010Q

Optimum No Rinse Wash & Shine - 32 oz. - NR2010Q

Clay Works Wonders

Another chemical solution to your problem is clay. Car waxing clay is a high-quality way to leave your car with a beautiful polish. It’s also the perfect solution to hard water and navigating around water spots.

It’s our personal go-to for water spots on windows. It takes off the spots without doing any damage to the glass.

You’ll have to read the individual instructions that come with the clay product you purchase. Many options require you to add a secondary lubricating fluid to complete the process.

Polish Your Car After

General car polish can eliminate water spots too. It works two-fold since it also leaves your car with an incredible shine.

The polish that I recommend doesn’t soften your clear coat when you use it. It’s a non-abrasive mixture that simply polishes your car. You apply it to a microfiber towel and apply it generously to your car.

Once the polish dries, you should be left with a spotless clean — literally.

Wiping down car with microfiber towel

Use an MDR

A mineral deposit remover (MDR) was made specifically to attack water spots. I really like the MDR from proClean since it actually worked when I used it. You don’t need to buff it to apply, you can just use a soft sponge or towel.

It feels like a “wax” when you apply it. It goes to work and starts removing the water spots from your car. After a little, just wipe away the mixture, and voila.

Make sure you wear gloves because this MDR is slightly acidic. It won’t eat away at your clear coat, but it’s not great to get on your hands.

The best solution? Hit your car with an MDR then give it a good wax and seal after.

GlasWeld ProClean Hard Water Spot Remover Kit – 8 oz. Bottle with Applicator Pad – Mineral Deposit Remover

GlasWeld ProClean Hard Water Spot Remover Kit - 8 oz. Bottle with Applicator Pad - Mineral Deposit Remover

Try a Portable Water System (Heavy-Duty Solution)

If you’re serious about your water cleaning, you can grab a portable water system. This is recommended for people who run small car washes or very frequently wash their personal cars.

This process is called de-ionization. It takes the ions out of the water before spraying it out of a hose. One of the big targeted ions is general “minerals” that lead to hard water.

The result is pure H20. Good enough for Bobby Boucher to use (any other Waterboy fans out there)?

It costs a few hundred bucks, but it will de-ionize up to around 300 gallons according to their site. They don’t just soften the water; they actually pull the minerals out of it and remove harmful ions. Your car will love the new water.

Simplest RV & Car Wash Kit, Spotless Rinse Works for All Vehicles

Improve Your House’s Water Softening System

Speaking of softening water, maybe it’s time to take a look at your home’s water-softening system. If you live in an apartment, just ignore this tip.

If you own your house or rent it and deeply care about your water, you can install a full softening system. These systems typically target calcium and magnesium in your home’s water. These two minerals are the big offenders when it comes to water spots.

The great part? This softens all the water in your home, not just the stuff you use to wash your car. Water that comes out of your tap will be safer to drink at the end of the day.

I’m not gonna lie, one of these systems can get pretty pricey. It also requires professional installation so nothing goes wrong. Still, it does much more than just prevent hard water spots, it improves your quality of life.

Water softener
How a water softener works.

Hit Up Your Local Car Washer

If all else fails and you want a quick and easy answer, you can just cruise to your local car wash. It’s pretty much guaranteed that their water will be soft enough for washing cars.

The best option is one of those automatic car washes. Their mixture of waxes, sealants, and soaps does a great job of removing water spots and preventing them after the wash.

It always helps that they typically dry the car right after washing it. As I pointed out, immediate drying helps prevent spots as well.

You’ll have to talk to your car wash spot to see if they have a membership program. A lot of places offer unlimited washes for a monthly fee. More than a handful of washes a month and you’ll come up way ahead.

Vehicle Cleaning car wash

Preventing Hard Water Spots in the Future

After getting your car nice and shiny, you probably want to avoid wasting time in the future. I have a few tips to help you prevent hard water spots next time you wash your car.

Get a Lighter-Colored Vehicle

This idea might seem pretty crazy, but lighter-colored vehicles can hide water spots a lot easier. I wouldn’t suggest painting or wrapping your car just to avoid water spots, but maybe you could go for a white car next time you buy or lease a car.

Quickly Dry Your Ride

If you want to break up the mineral party before they can get together and make water spots, you’ll need to quickly dry your car.

This isn’t a guarantee that you won’t see any water spots, but it’s a great way to minimize the spots that you do get. After washing your car, quickly grab your microfiber towel and dry off your vehicle.

If there are beads of water left on the car, there’s a good chance that you’ll get a water spot there, after it dries.

Car wash worker wipes the car after washing with microfiber towel. Professional car wash
Dry the vehicle with a microfiber towel after the car wash.

Use Some Wax or Sealant

A nice ceramic wax and sealant will work wonders. Applying it to your car from time to time is a quick way to avoid water spots in the future.

It adds a top layer to your paint that protects against drying water. Even if you do get water spots, it’s a lot easier to remove them from the layer of wax than from a rough, unwaxed clear coat on top of your car.


Hard water isn’t a death sentence when it comes to water spots on your vehicle. I went over some ways to avoid water spots, clear them once you have them, and optimize your car cleaning experience. Check out the other recommended cleaning products. Also, be sure to explore the rest of this blog for more car care tips.

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Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

4 thoughts on “How To Safely Wash a Car with Hard Water”

  1. I’ve been washing my own car and have had issues with car soap that doesn’t lather well or water spots forming no matter the materials or brands I’ve used, that means I must’ve been washing car with hard water. But thanks for your article, I have know to reducing the hardness of water and using soft water for washing cars.

    • Hi Jessica, thanks for checking out the article. In my experience using a microfiber towel to wipe the vehicle dry as quickly as possible after using hard water helps reduce water spots etching onto the surface of the vehicle. I recommend using wax or sealant afterward to help protect your car’s paint from any outside elements.

    • Hi Jessica, thanks for checking out the article! Generally, hard water should be avoided since it can cause issues with the paintwork of the car. In this article, I cover what precautions to take when hard water is used because many car owners use it unaware of the possible issues that can arise from using it.


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