Grit in the rinse water?

[SR99]

My car was fairly dusty, built up over a couple weeks, so instead of just using UWW+ at home, I decided I'd go to the self-serve car wash and blast the dust off the paint and wheels just using the rinse setting, then spritz it with UWW+ to wipe it dry.

I ended up getting some linear scratches, like you'd get if you were dragging some light grits in your wiping towel.

Now I can't be 100% sure the grit was in the rinse water from the car wash, but I think I recall people saying some car washes recycle their water (which may not be a bad thing, depending on their filtering/purification process). Grit in the rinse water would be my guess though.

Maybe I should have used their "spot-free rinse" setting (the water only trickles out on that setting) but I was afraid they might put some chemical additive in that stream. Not sure...anyone know?

Anyway, it got me thinking, it's entirely possible there could be grits in the municipal water supply at home. The water travels many miles through some pretty old pipe that may have cracks in it. Back before I started using predominately rinseless, I used to use an inline mineral filter on the hose due to hard water, but never thought that might also serve as a small grit particle filter too.

Does anyone else use a filter on the municipal water supply from your spigot?

[Desertnate]

If the water is recycled there could be some grit in it. However I think there was still some grit on the car when you did the waterless wash and that is your problem.

This winter, I tried to do a touchless washes followed up by a waterless wash when I attempted to clean my car. However, I found that when the car was heavily salt crusted there was still a very faint layer of dust/grime remaining. The remaining layer of grime then caused marring/swirls when I did my waterless wash. On at least one occasion, I could see it happening while I worked. This might be the same situation in your case.

I've never been able to achieve much with a self-serve car wash. After dumping loads of quarters into the machines I still pull out the other side with more grime on the car than I would like.

I've never had issues when doing a bucket wash. Any marring/swirls were my fault and can be linked to a mistake I made. Not the water coming out of the hose.

[kevin_1981]

I'm just a newb here, but I would be hesitant to believe that there would be grit that was in the car wash's equipment. The size of the nozzle on pressure washers is so small that if there was grit in there, those heads would probably be getting clogged. I agree with everything desertnate said. Just my $.02.

[Audios S6]

A quick google search found a website for one particular reclaim system, they had data from tesing performed by the local wastewater agency. It's unclear where the sample was taken from in the process, but it identified 219 mg/L total suspended solid, which would be any grit as well as precipitates and sludge. So there is the potential. But you should expect some grit in your city water or well water as well. City water should be far below 219 mg/L, closer to 1-10 mg/L from anything in the city main.

[SoonerGM]

just think about water spots. maybe it's not "grit" but there are calcium, lime deposits, and other minerals in most forms of treated water. in my opinion if those deposits are that hard and visible upon drying, then they are hard enough to create scratches and marring to the paint as it's being wiped off of your paint.

[SR99]

Thanks for the comments. I guess I'll never know the cause for sure.

As far as the grit size, it's not the size of the grit that allows it to scratch, it's the hardness of the material, sharpness,etc. Very fine abrasives that are physically very small can scratch paint.

Does anyone know if there are chemicals added to the "spot free rinse" at self-serve car washes?

[Setec Astronomy]

Does anyone else use a filter on the municipal water supply from your spigot?

Yes, I have a 5 micron whole-house filter.



just think about water spots. maybe it's not "grit" but there are calcium, lime deposits, and other minerals in most forms of treated water. in my opinion if those deposits are that hard and visible upon drying, then they are hard enough to create scratches and marring to the paint as it's being wiped off of your paint.

Sorry but before that drop of water dries out, those minerals are simply ions in the water. So maybe they are hard enough to "create scratches and marring" but I doubt you'd be able to see scratches 1 molecule wide.

[SoonerGM]

Sorry but before that drop of water dries out, those minerals are simply ions in the water. So maybe they are hard enough to "create scratches and marring" but I doubt you'd be able to see scratches 1 molecule wide.

Why be sorry, that's pretty good information.


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[FUNX650]

Almost sounds like a title of a Country song.

"Well the Wife took up with the preacherman
down at Junction City First Baptist Church.
And the Tyler boys stole my pickup truck,
and wrapped it around that thar big ol' Birch.

For these events I will hide my pride
And try to take it all in stride...

For the thing that will cause me to pause
And think about committing manslaughter:
Is when I find out that my hometown Car Wash
Has got: Grit in their dang rinse-water!"

George "Bob" Jones

[Setec Astronomy]

Why be sorry, that's pretty good information.

Well, people talk about "filtering" out hardness in water. You can filter out particles, but hardness in water is ions (atoms/molecules) which are way too small to be filtered. They are "filtered" out by ion exchange (softener) or ion removal (deionizer). Of course you can also purify water through distillation or remove some large molecules by reverse osmosis or certain compounds by carbon filtering.

[swanicyouth]

I wash my car like this a lot and haven't had a problem with marring.

How much UWW did you use?

Which towels odd you use?

What color / make is the car?

I think blaming it on the water is a long shot. It's more likely just marring from a waterless wash due to various possible factors in the wash process. I'm pretty sure "spot free" water at the Pay N Spray is just softened water - not water with creepy chemicals or DI water (would cost a fortune). I've used it many times without issue.

[SR99]

I wash my car like this a lot and haven't had a problem with marring.

How much UWW did you use?
It was mixed .5 oz in 22 water in a spray bottle, and I sprayed it atop the beaded water from the rinse, roughly a "2 trigger pull" coating of each portion of the surface (e.g. about 10-12 trigger pulls for the roof). That's less that I use for a regular waterless wash but it didn't seem like I would need that much lubrication given I just blasted all the dust away

Which towels odd you use?
I think they're called Chinchilla (double sided thick nap, black with red border) and also used Uber Ultra (light blue with dark blue border, single side thick nap) for the final pass. These are my dedicated waterless wash towels.

What color / make is the car?
Audi, metallic white. In 2-1/2 years of cleaning this car (using UWW+ 90% of the time, same MF towels) I've never gotten fine scratches like this. The car was not dirty, just dusty, and had a good layer of sealant underneath. The high pressure rinse appeared to rid the surfaces of everything (except some brake dust splatter behind the front wheels which I spot cleaned), and it's hard to imagine there were remaining stuck grits given it was just dusty to start with.

I think blaming it on the water is a long shot. It's more likely just marring from a waterless wash due to various possible factors in the wash process. I'm pretty sure "spot free" water at the Pay N Spray is just softened water - not water with creepy chemicals or DI water (would cost a fortune). I've used it many times without issue.

Yep, could be. I suppose it's also possible the grits blew in (it was a tad windy), or my MF towels somehow got contaminated. If you or anyone sees something in my process I could change let me know. It seems to have worked well for quite some time, and the only thing I changed in this case was going to the DIY car wash for a pre-rinse. Maybe it was just a fluke.

[swanicyouth]

Sounds like your using good towels, as I've use Chinchillas before without issue. When I was asking "how much WW did you use", I was asking how much volume to do the whole car.

As time goes on, and the weather gets better I use this pre-rinse waterless wash method more and more frequently. Its faster, requires dragging out less junk, and the car comes out perfect.

To do my SUV, I use about 48oz of UWW+. I really use a lot of solution, the panels are dripping soaking wet. I also pre-spray a dry towel side with solution.

I would recommend buying a good waterless wash with a high dilution like Pinnacle or UWW+ by the gallon. That way you will be able to make tons of it forever. I also prefer using the pump sprayers (instead of spray bottles) to load up the panel with a lot of wash solution.

I usually use a back and forth "S" style pattern when wiping the panel going from cleanest to dirties area. My technique is nowhere near perfect though, and I've found if the towel is a bit soiled you can use it as a first pass towel on dirty glass.

However, I don't use this method on my black BMW. I've done it a few times, but I still think 2BM washes are just safer and will always cause less marring. A white car I would use this method all the time though.

If your still interested in doing this method, I would try ditching the spray bottle and getting a pump sprayer. Use a lot of solution, and even spray solution in front of the towel as you go down the panel. The pump sprayers AG sells are great and basically bullet proof. The spray pattern is infinitely adjustable and they hold pressure for months.

Also, I use waffle weave towels to dry, but instead of using like some 4'x4' towel folded over a million times, I use a few 16"x24" folded in 8s. First time I see any sign of dirt on the drying towel - I switch to another side.