Is salty water reused in car washes?

BriteBlue

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Just thinking about winter & washing the car and remembered saving the links to these articles from last year. I found them & thought I’d pass along the information. Also did a cut/paste & posted the articles in case the links stopped working.

http://www.chicagotribune.com/classified/automotive/sc-auto-motormouth-0301-story.html

March 4, 2018

Q: I just had my car washed at a popular local facility. I watched almost every customer hit the “free” under-carriage rinse button. Could that rinse water be recycled from the wash process? This time of year with so much road salt being washed away, I wondered if we were getting a “salt water rinse.” I imagine that would simply hasten early rust and corrosion. What do you think?

A: We turned to Eric Wulf, the CEO of the International Carwash Association, who stated: None of the water that is reused and recycled in the wash process is unfiltered. Meaning, the water used for undercarriage washing is going to be filtered of much of the salinity you fear — certainly it will have much less salinity than the “raw salt” sticking to the underside of the vehicle.

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http://www.chicagotribune.com/classified/automotive/sc-auto-motormouth-0322-story.html#

March 25, 2018

I just read your column “Is salty water reused in car washes?” As a retired chemical marketer who has dealt with salt solubility issues, I suggest you look further into the issue of whether there is appreciable salt in recycled car wash water. I fear that Mr. Wulf is misinformed if he believes that filtration removes most of the salt from recycled car wash water. Most road salts are either sodium chloride (rock salt) or sometimes a concentrated solution of calcium chloride in colder weather. Sodium chloride only precipitates (falls out of solution as a filterable solid) above about 23-26 percent. Below those concentrations salt cannot precipitate. And the warmer the water gets, the higher the soluble salt concentrations can get. While filtration can remove much of the solids (dirt and grit) from recycled wash water, it can only remove solids. So even recycled filtered water can still contain salt.

A: Thanks to you, S.B. and several other readers who know their chemistry. About the only true way to remove the salt is through distillation or reverse osmosis. Nevertheless, rinsing the undercarriage with saline solution is better than allowing the buildup of salt to eat away at your Edsel.

We reached out to Eric Wulf, CEO of the International Carwash Association, for clarification.

He stated: “Good readers! Most car washes have, essentially, three types of water: fresh (from the municipality), recycled (that has been filtered, either cyclonically or biologically) and reverse osmosis. Some can actually have a fourth — rainwater recapture. Reverse osmosis would be the most purified water, similar to many home filter systems. Reverse osmosis is used as the final rinse, to make sure that the car will dry without spots. It is usually not used for undercarriage washing.

“It will depend upon the car wash you visit, which of the above mix you are getting — but you are likely getting all three for the undercarriage wash. Some washes will feed the undercarriage with fresh water, so in that case the salinity would be low already. But even for those that don’t, they are using a mix of fresh, recycled and reverse osmosis (since that is recaptured by the recycling system), which means that the overall salinity of the undercarriage wash water will be better than the salt sticking to the car! No, filtration doesn’t remove all the salt but the processes that go into the mix of the wash water — filtration, reverse osmosis and fresh — means that salt is quite diluted.

“It’s also not uncommon for operators to add a rust inhibitor to the undercarriage water.”

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SDAlexander8

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Automatic car washes are the devil. Unless it’s touchless, of course...
 

Gruber

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I have only used a primitive manual car wash for my car. They don't have any water recycling or filtering facilities, so the water they use can only be the utility fresh water.
Removing salt from water by any method would be more expensive than buying utility water, so it's impossible except for very small amounts of final rinse. Yes, in very salty road conditions rinsing with salty water might still be of benefit, on the condition that you would then rinse again with fresh water at home after the commercial car wash....:bump:
 
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BriteBlue

BriteBlue

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Here's a thought - high pressure salt water is now being forced into nooks & crannies where previously there was no salt.
 

shoegazer

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I use the DIY pressure wand car washes. But I always wonder if the operator will be tempted to just buy a bunch of dish soap from Cosco instead of the real car wash soap.

I need to find a decent home version of these things.
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