Which water is Best for Coolant

If you’re someone that likes to take good care of your vehicle by yourself, you’re sure to come across the need to keep the cooling system of your car in a top-notch performance state. That is where you’re sure to be hit with a lot of confusion and even more misleading answers to them.

It is common knowledge that car oils need to be changed, and the know-how of the process is also well-known in the community. Less common knowledge is that engine coolant also needs to be replaced. A lot of confusion arises here, as to which type of water you should be using for your coolant.

Get your hands on the proper coolant!

A lot of coolants can be fit for many cars but that does not mean they will be fit for your specific car. So, before you get started with anything else, we suggest you take a proper look at your manufacturer’s manual and check the specifications for your car. Accordingly, you should get the proper coolant for your vehicle.

Now that you know which coolant works best for your vehicle, the next question is, which water is the best to use for coolant? Some people claim tap water works fine for them while some justify that distilled water is the best.

To clear up all your confusion about which water you should be using in your coolant, we will walk you through all the possible options and why you should be avoiding or preferring them.

Avoid Tap Water for Coolant at All Costs

If you’re fairly new to maintenance, you’re going to have this question. Can I use tap water with engine coolant? The answer is a big no. To back this up, we have a good justification for you.

The reason for avoiding tap water is that it contains impurities and minerals. Regardless of where you live, tap water is never mineral free and will contain mineral deposits in it by nature. Tap water will form mineral deposits in the radiator over time.

If used repeatedly, your radiator will build up calcium and magnesium deposits. Once the radiator has this kind of buildup, it becomes less effective, bringing the cooling system performance down drastically.

If you have the choice of using distilled or deionized water, we suggest you go for the other options rather than having to use tap water.

So, Is Distilled Water the Right Choice?

Even though better than tap water, distilled water is not the right choice either. You’re going to be recommended distilled water by a lot of people, even people who are in business. Now, you’re probably wondering why distilled water is a wrong choice when the minerals in it are stripped away.

During the distillation process, the minerals are stripped while unbalancing the remaining solution. This happens because the minerals (calcium and magnesium) take electrons from the solution. Now when this unbalanced water enters your radiator, the metals in your radiator are put at risk. Any metal the water will come in contact with will try to strip electrons from it to balance itself.

When distilled water is used repeatedly, the metals in your radiator will eventually be damaged.

We suggest you avoid distilled water as much as tap water, as it can be as destructive for your cooling system as tap water, just in a different manner.

Use Deionized Water for Coolant

The best option for your coolant is deionized water. Comparative to distilled water, this water comes with all mineral ions removed. Deionization of water allows the minerals to be stripped from the water first leaving behind the mineral ions and the remaining solution. Once that is done, the mineral ions are also removed from the solution, leaving the water in a stable, mineral-free state.

When used as a coolant, unlike distilled water it doesn’t strip the metal in your radiator which can lead to corrosion. This allows your cooling system to have better performance and a longer lifetime.

Where can you get Deionized Water?

There are a handful of places you can get deionized water from. The majority of chemical manufacturers provide deionized water for consumer purchase at supermarkets. You can get your hands on it from Amazon and eBay as well. However, when purchasing, make sure to check if the manufacturer is reputable and reliable.

Can you make your Deionized Water at Home?

If you are a DIY type of person and have some extra time at hand, you have the option to make Deionized water yourself!

All you need to do is:

  • Filter your water, removing all organic wastes from it.
  • Get your ion-exchanging resins ready
  • Connect the ion-exchangers to your solution
  • The ion-exchange resins will attract all impure ions
  • Your water will be left deionized and ready for use!


To sum it up, people tend to get overwhelmed by the amount of misleading information when it comes to water choice for coolant. Even though it may sound simple and one might not bother diving into the discussion, the choice you make leads to how well your cooling system performs and its lifetime. In this article, you will be briefed on why you should avoid certain water types and why you should choose the best suitable type.

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