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Your Car and Hard Water Spots

Wednesday, March 31st by Mike Ohlinger


Girl Washing Car

Along with pastel-colored dress shirts, birds making nests in inopportune locations, and the first signs of those weeds you thought you killed last year starting to poke through the decorative pebbles near your front walk, spring marks the beginning of carwash season. Where winter carwashes were all about utility in the northern states, in keeping the road salt from eating a hole in your door’s side panel, spring carwashes are all about showing off the family coupe in your driveway to your neighbors, or perhaps for most of us, it’s polishing up the minivan pretending it’s something a little sleeker, a little faster.

Washing your car at home can be a nice way to spend an afternoon outside, especially if you like to take extra care making sure there are no missed spots. But, unless you’re an expert with the drying rag and catch every last drop after the final rinse with the hose, you may notice that after a wash at home, your car is left spotty or streaky, especially on glass surfaces. Why does this happen and how does a spot-free rinse at a ten-dollar carwash eliminate this issue? And, more importantly, can you replicate that spot-free rinse in your driveway at home?

What causes those spots?

The annoying spots leftover on your car after washing are the result of hard water deposits. Hard water contains dissolved minerals like calcium and magnesium. When the leftover water droplets on your car evaporate, they leave these minerals behind, causing those off-white spots and streaks.

Hard water can be treated at home by using a water softener, which uses resin beads and a process called ion-exchange to capture the minerals that make up hard water while releasing a small amount of sodium in the process. However, many homes with water softeners installed do not send their treated water to outdoor water fixtures since soft water is rarely needed outside. And even if you did, the harmless sodium that replaced the hardness minerals will also leave a residue once the water evaporates.

So, based on the knowledge of what is inside the hard water that comes out of your hose, it’s safe to assume that in order to eliminate those leftover spots, you should be using water that has the least amount of minerals in it for your final rinse. How do carwashes that process hundreds of cars a day pull this off?

Reverse Osmosis

In water treatment, one of the processes used to create the best, most impurity-free water is called reverse osmosis. Most common in home drinking water systems, a reverse osmosis treatment unit is usually placed beneath a sink and consists of several filtration elements, including pre-filters, a membrane, and post-filters. Water is forced through the membrane, which filters out extremely small particulates, and supplies a holding tank until it is ready to be drawn from a tap at the kitchen sink for drinking.

To obtain that clear, spot-free rinse, carwashes have larger versions of those in-home reverse osmosis units to treat bigger volumes of water.  After your car has been washed and scrubbed, automatic car washes use a final rinse of reverse osmosis water to wash away any residual soap, cleaning agents, and cleaning water. This impurity-free water is then able to be easily dried and can evaporate without leaving behind any of the minerals that create spots and streaks.

A Spot-Free Rinse At HomeDrying Car

If you have a reverse osmosis unit at home, you can replicate that automatic carwash spot-free rinse in your driveway by pouring reverse osmosis water during a final rinse, after you’ve rinsed off soap using the hose. This final rinse of reverse osmosis water will wash away any of the remaining soap or hard water on your vehicle. A final wipe with the rag will help your car dry faster, but missing a few drops of reverse osmosis water will not lead to any of the annoying spotting or streaking that hard water, or even soft water drops can leave behind.

Granted, using a few gallons of reverse osmosis water from your under-sink unit can be kind of tricky. Reverse osmosis water takes some time to generate through its filtration system --- so drawing even one gallon to rinse your car will take some effort. Of course, if you're an enthusiast, there are whole-house reverse osmosis systems that treats water at the point of entry as well. To replicate the reverse osmosis quality without waiting at your RO tap, an alternative is using distilled water, which can often be purchased in larger quantities.

If you’re interested in stepping up your at-home carwash game or are looking for a better drinking water solution, contact your nearest WaterCare dealer to discuss reverse osmosis solutions. A WaterCare water treatment expert can help you fix those hard water problems and supply you with a hard-working reverse osmosis unit that’s perfect for your family (and for giving your car a little extra shine). Call us today!

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