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Can I Use Rainwater to Wash My Car?

can i use rainwater to wash my car

When it comes to saving water, whether that’s to help the environment or for some other reason, it’s pretty understandable to assume that rainwater could help you cut down on water usage. After all, rainwater is already in the environment and doesn’t cost anything to make use of. In fact, why not use it? May as well, right?

That said, can you use rainwater to wash your car? Yes, you can use rainwater to wash your car, but it is not a good choice as rainwater tends to pickup pollutants and contaminants in the air. 

Note that we aren’t saying that rainwater can’t clean your car to some extent, but is it a better option than water from your hose? No, no it is not. The main benefit is that rain is free, but there are many downsides to using it, even when you collect it in a rain barrel.

Is Rainwater Bad For My Car?

Rain isn’t inherently bad for your car, but it has the potential to be. It depends on a number of factors. The main problem with rain is that it picks up contaminants in the air.

This includes dust, dirt, pollen and all sorts of other particles that could scratch or mark your car when washing with it, especially if you’re scrubbing that water into the paint.

The problems are compounded if you live near factories, power plants, or other places that spew pollution into the air. In those areas, rain often contains sulfur dioxide or nitrogen dioxide, creating ‘acid rain.’ Needless to say, you don’t want to wash your car with that.

When the rain on your car evaporates, the particles and the acid it carried is left behind on your car. When it comes to chemicals in particular, direct sunlight on those acids can “etch” them into a car’s finish, leaving behind little marks that look like spattered raindrops. Once this happens, those blemishes can’t be removed by washing the car.

Now, you could filter the rainwater you collect via barrel. But that doesn’t mean you’ll be able to get all of the aforementioned bad stuff out of it.

To get that acid out, you’d need very thorough and expensive filtering capabilities that would probably require dozens or even hundreds of cheap carwashes to make worth it.

We recommend using a rain barrel that is leak-proof and has a high capacity if you utilize rainwater for many daily chores. This collapsible rain barrel by Vingli is high-quality, portable, and reusable. It comes in 50, 66, and 100 gallon tanks.

Should I Let the Rain Wash My Car?

Well, considering the things we just talked about, probably not. However, there’s a difference in actively washing your car with rainwater that you’ve collected and just leaving your car out in the rain and calling it a car wash.

Even so, the answer is still no. Remember what we said about acid rain evaporating and leaving blemishes you can’t wash away when the acid bakes in direct sunlight? Well, that’s still going to happen if you just leave the car in the rain, and then the sun.

Now, your car will probably look cleaner immediately after a shower because the rain will wash off some of the dirt and grime on the surface of your vehicle.

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But this is misleading: for one, as we said before, when that rain evaporates it will leave acid or particles behind, so once the rain dries your car will look dirty again.

Secondly, rain doesn’t have the cleansing power to provide a deep clean or conditioning for your car. If you think it’s going to take care of all those bug guts, think again. A real carwash, whether you do it at home or a service, uses soap with special forumales that have the required features to deep clean and protect your car. Rainwater can’t do that.

Finally, it’s worth mentioning that the rain isn’t going to clean the undercarriage of your car, which is also something that needs to be cleaned. Dirt and salt in the undercarriage can corrode it if it isn’t cleaned properly. Just letting your car sit out in the rain won’t do that.

Rainwater and Contaminants

All water is not equal. It may seem like rainwater is a valid substitute for a real carwash, be it at home or at a business, but that’s just not true. Sure, you can wash your car with rainwater, but not only will it do a poor job, it may even damage the car.

Rain carries particles and chemicals from the air, and those things are left behind on your car when the rain evaporates. This means your car will look cleaner immediately after rain, but when the water dries it will look dirty again: it might even be dirtier than it was before.

Even if you collect rainwater, filtering isn’t going to catch everything: particles could scratch your car, and the chemicals from acid rain could etch into the paint, unable to be removed. Moreover, rainwater doesn’t have any of the special soap used for cars that cleen deeply and protect the paint.

Leaving your car in the rain doesn’t do much either. Rainwater doesn’t have enough cleansing power to get rid of things like bug splatters, especially if you aren’t scrubbing. It will often leave your car looking streaky, and it does nothing to clean the undercarriage of your vehicle, which can be corroded by dirt and salt.

Final Thoughts

Ultimately, you can clean your car using rainwater. However, there’s little to no reason to do so. Rainwater may be free, but it doesn’t clean very well: in fact, it can be dirty and make your car dirtier than it was to begin with.

That being said, the traditional car wash is a far better idea. Whether you do it yourself or go to a business and pay a few dollars, your car will receive much better treatment and be cleaned far more thoroughly.

Still, if you absolutely had to clean your car with rainwater, you could technically do it. We just don’t recommend it, for all of the above reasons.

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