Washing Your Car with Hard Water? 3 Spot-Free Solutions

Hard water is something that I grew up with when washing my first car, and it can be a pain. No matter how hard you try to quickly remove them, hard water spots seem to always stick around and can make your vehicle look almost dirty in a sense.

In this blog, I’ll share a few tips for dealing with water spots from removing them to preventing them altogether.

Solution 1: Prevention

wax to prevent hard water spots

There is no real ‘guaranteed’ way to prevent all water spots all the time (without treating the water itself), but there are a few things that you can do to help prevent them with a few basic products, assuming that your water isn’t too hard.

There are also solutions that can help eliminate them altogether if treatment isn’t effective.

The map below shows the states with the highest grains per gallon (GPG) in dark blue. Keep in mind that if you live in states with heavier concentrations of minerals, there may not be much you can do about hard water in terms of prevention, but it can be treated.

hard water in us

Source: Culligan Lansing

Fun Fact: The six metro areas in the United States that are hit hardest by hard water are: Indianapolis, Las Vegas, Minneapolis, Phoenix, San Antonio, and Tampa.

Option 1: Dry your vehicle quickly

Based on my own personal experience in dealing with hard water, it is definitely worse when you let hard water dry, but wiping your car down quickly (especially on a hot day), can help reduce the chances of etching into the surface after drying.

When hard water dried, it may also produce a powdery substance in extreme cases, so it’s always good to wipe away to beads of water before this can occur.

Option 2: Opt for a lighter color vehicle

Okay, so not a way to really prevent them, but it is great for making them less noticeable. Midtone silver or pewter colors are typically the best for hiding spots, and is something to keep in mind if you are in the market for a new vehicle and live in an area where you deal with hard water.

Option 3: Protect your vehicle with a wax or sealant

One of the most effective ways to prevent hard water is to use a good carnauba wax or sealant. The purpose of these products is not only to improve luster or shininess, but really to protect your paint from the elements by providing a glossy layer of protection that repels water.

If water spots do form on this wax layer, they are much easier to remove as opposed to being stuck on a rough, unwaxed clear coat.

Solution 2: Removal

white vinegar remove hard water spots

If hard water is a continuous problem, there are a few techniques you can use to remove them. These minerals are not organic, so acid-based cleaners will be the most effective.

Okay: Acidic household products like white vinegar

This is a household method that works pretty well for minor water spots, but may not be effective for everyone. Fill a spray bottle with 50/50 white vinegar and water and test a small area first.

For harder water spots, try letting the vinegar soak for a couple minutes before wiping away.

Vinegar is slightly acidic as are citrus-based cleaners which is why they are commonly used for spot removers when diluted properly. I have seen people use diluted wheel acid, but would not recommend it for the average person since it’s honestly not practical unless you have an extreme case.

Always protect yourself with a mask, gloves, and goggles when dealing with stronger chemicals. I recently outlined everything to know about using respirators and masks for detailing you can check out here.

Good:  ONR (Optimum No Rinse)

If you are washing your car in the winter, ONR is a great product to try that can also help remove water spots. Since no rinsing is required, many people use this in a bucket or spray bottle mixed together with water.

One tip that I have heard helps remove hard water spots is to try hot (or warmer) water on harder stains. While many people don’t use warm water for regular car shampoo (to prevent soap from drying), ONR acts as a softener and may work better in this case. Give it a try.

Good: Clay

For superficial water spots that aren’t baked into the clear coat, clay can be a good option for removing some spots, but not all.

While it does help remove industrial fallout and metal fragments, embedded (etched) particles that have been on your car for so long that they have begun to penetrate the clear coat, will require compounding or polishing to remove.

Clay works great on windows if you have water spots, since there is no superficial layer for these particles to get trapped. As always, be sure to use proper lubrication with clays.

Better: Basic Car Polish

polish to remove hard water spots

A regular car polish is generally one of the best ways to remove stubborn hard water spots if you already have a polisher.

Anything abrasive like a compound or polish can soften the clear coat with repeated use, which is why it’s best to use something non-abrasive for most cases. If etching has started, it may be your best option.

This video did a great job of explaining a few of the water spot removal techniques in greater detail:

Best: Optimum MDR Mineral Deposit Remover

This usually does a better job at removing minerals that are embedded deeper into the paint, since is formulated for exactly this purpose. It is slightly acidic, so it’s important to wear gloves. You apply it sort of like a wax, where you let it dwell on the surface for a few minutes, and wipe away.

Using a polish to smooth out any imperfections, followed by a good sealant or wax should yield you the best results when using MDR.

Solution 3: Elimination

de-ionization hard water spots

Even if you do have hard water, there are a couple of common ways to prevent this from happening. Testing the pH of your water for high concentrations of minerals before and after filtration can really illustrate what a difference these devices make.

Option 1: CR Spotless Portable Water System

Out of both of the options I recommend, a spotless portable water system is probably the most affordable for most people that are simply washing vehicles. This device works using a process called de-ionization, which is the process of removing charged particles (salts and minerals) in order to release hydrogen and oxygen (impurity-free water).

To learn more about these benefits and uses of purified water, check out a post I wrote: Deionized vs Distilled Water for Detailing – When to Use It!

This entry-level single filter (resin) system by CR Spotless here on Amazon will provide around 150 gallons of water, which can last anywhere from 10-20 washes depending on how much water you use. Some people will it as a spot-free rinse, while using harder water to apply soap, but it really depends on your water quality.

Griots also makes a similar portable de-ionized system for around the same price point.

Keep in mind both of these units are demineralizers, not softeners. They basically remove (not just soften) and are ideal for washing vehicles.

Option 2: Household Water Softening System

Softeners, on the other hand are simply used to remove calcium, which can be a large part of what makes hard water. Softeners basically convert calcium and magnesium (which can cause more noticeable water spots), to sodium or potassium which should spot a lot less.

These units typically last a lot longer, and are a great solution for getting your glassware shiny again, reducing water spots on shower doors, etc. If you want the added benefits softened water can have throughout your plumbing indoors, this may be the best solution.

While not as effective as de-ionization, it still should help to improve the TDS levels by up to 95 percent, and basically eliminating those very noticeable spots.

How Hard Water Spots Form

hard water spots on car

Hard water is a result of dirt and minerals being carried to the surface of a well. Magnesium and calcium are a couple of the most common and is pretty much a result of water and limestone interacting underground. While not harmful to your health, these minerals that are left behind can make your car look very dirty.

I’ve found the most visible hard water spots occur when water I didn’t intend to hit my car (like a sprinkler) has a chance to dry in the baking sun.


When dealing with hard water, it really comes down to prevention and elimination. Removing hard water spots every time you wash can be a pain, so just be sure to protect the surface of your vehicle on a regular basis to create a barrier between clean, naked paint and any harsh minerals in your water.

Prevention and/or treatment is probably the best course of action for most people, but if these methods aren’t cutting it, definitely try a filtration method.

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