R.O. water for coolant flush

Joined
Jul 9, 2018
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203
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SK, Canada
My town has a R.O water system.
Would R.O. Water be suitable to flush coolant from vehicle?

There is still chlorine added, & probably fluoride.

I have a TDS monitor to measure the TDS in water.

Prior to the town instaling this R.O. System I had an undercounter R.O. system as well.

I could get the TDS under 5 ppm. usually around 3 ppm.

I have a 2018 Ford F150 with the Orange cooant, & I think now they are using a yellow, which are supposed to be compatible anyway.
 
Joined
Apr 27, 2010
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Suburban Washington DC
No idea what RO water is, but how much does 15-20 gallons of distilled water cost in the scheme of things? Like $25? If that's gonna break you, why own a 2018?
 
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Reverse osmosis, deionized, or distilled water is fine. They all remove hardness from the water. Chlorine and especially fluoride are not a concern.

So much misinformation and Internet conjecture on this. You find entire websites devoted to how one method is the devil's spawn whereas another is nirvana. None of them apply here.
 
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MI
You don't think the chlorine and fluoride might interact with the coolant chemistry? Most times, about half the total coolant capacity is in the engine block. In a 10 quart system, you will have approximately 5 quarts of the chlorine/flouride water left to mix with the coolant. It's something I would not guess about (I'm not a chemist)..
 

JHZR2

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To flush it’s probably ok. I’d want to get as much of that flush water out though before reintroducing coolant…. At $1/gal for distilled most anywhere it’s not that big a deal to get some.
 

JHZR2

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You don't think the chlorine and fluoride might interact with the coolant chemistry? Most times, about half the total coolant capacity is in the engine block. In a 10 quart system, you will have approximately 5 quarts of the chlorine/flouride water left to mix with the coolant. It's something I would not guess about (I'm not a chemist)..
Maybe so, maybe not. Engines have block drains for a reason.

If I were actually trying to do a flush I’d do multiple repeat times, so the last one or two I’d just run distilled and then no big deal.
 
Joined
Jan 1, 2003
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Daytona Beach
The whole towns water is RO? That is amazing.
Same thing in Marietta Ohio. They did it to "solve" a nitrate issue that exceeded fed limits.
I suspect that some communities in FL have that system as well. Sometimes saltwater gets into the water wells that are near the ocean, not to mention very high sulfur (smelly) content in certain areas.

I put in an RO system in Ohio when I lived there. (Before the town installed theirs) Water was below 5 ppm hardness if it went through that system. I only used it for the refrigerator water/ice system. Sure made some good drinking water.

Should be fine for flushing a cooling system.
 
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Usa
I remember thus rislone webpage being the most official source saying distilled is wrong because hungry molecules absorb ur metals.
They say to use "softened water". Hadnt heard of that, but a search brings up stuff about r.o. so i use it. Car runs fine.

 
Joined
Dec 26, 2005
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I remember thus rislone webpage being the most official source saying distilled is wrong because hungry molecules absorb ur metals.
They say to use "softened water". Hadnt heard of that, but a search brings up stuff about r.o. so i use it. Car runs fine.

This is an absolute load of nonsense, and we've had discussions on here about it before. A classic case of someone having a tiny bit of knowledge and then extrapolating it into a mantra that is garbage.

Yes, metals will dissolve in distilled, deionized and RO water. And, those same metals will dissolve in tap water or soft water depending on the existing concentration. If there is low or no aluminum in the tap or soft water then exactly the same amount will be dissolved as in distilled water. Same for iron or any other metal. Water softeners do not remove aluminum but they do remove some iron, so this whole argument is silly.

The truth is however that this amount of metal is extremely small. We are talking about multi-kilograms of metal in an engine cooling system and micrograms of metal being dissolved. And not only that, since the system is closed once the water is saturated with the metal no more will dissolve. One would be hard pressed to think of a less technically significant issue than this. And on top of all this the coolant has passivation and anti-corrosion chemicals which help to prevent this in the first place, not that it is even significant.

Stupid and ignorant fear-mongering at its best. I wouldn't buy anything from those idiots just based on that crapola.
 
Last edited:
Joined
Dec 26, 2005
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Upper Midwest
Precisely. And this is why I've used good ol' tap water to flush my cooling systems for the past 30+ years. Get all the water out and the trace elements that may be left behind are inconsequential.
Tap water can be fine depending on the municipality. When we lived in the City of Milwaukee the total mineral content of the water was extremely low and was more than acceptable for cooling systems or even batteries. But here in the suburbs the hardness is very high on either private or city wells. There is zero reason to load the chelating agents in the coolant with your dilution water.
 
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Tap water can be fine depending on the municipality. When we lived in the City of Milwaukee the total mineral content of the water was extremely low and was more than acceptable for cooling systems or even batteries. But here in the suburbs the hardness is very high on either private or city wells. There is zero reason to load the chelating agents in the coolant with your dilution water.

Good points. I used to live on the south side with its wonderful Lake Michigan water. Was a different story in Oconomowoc back in the day with its well water. I didn't use that in cooling systems at all.

Let me revise by stating I've had no probs whatsoever with high-quality municipal water supplies.
 
Joined
Oct 23, 2017
Messages
1,101
Location
VA
My town has a R.O water system.
Would R.O. Water be suitable to flush coolant from vehicle?

There is still chlorine added, & probably fluoride.

I have a TDS monitor to measure the TDS in water.

Prior to the town instaling this R.O. System I had an undercounter R.O. system as well.

I could get the TDS under 5 ppm. usually around 3 ppm.

I have a 2018 Ford F150 with the Orange cooant, & I think now they are using a yellow, which are supposed to be compatible anyway.
Yeah, yellow is what you want to go back with following the flush. My 13 GT500 came with orange, I went through a lot of gallons of distilled water flushing that out of both the motor and intercooler systems then went to yellow.
 
Joined
Sep 2, 2005
Messages
9,247
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MIchigan
I remember thus rislone webpage being the most official source saying distilled is wrong because hungry molecules absorb ur metals.
They say to use "softened water". Hadnt heard of that, but a search brings up stuff about r.o. so i use it. Car runs fine.

Just look on any bottle of 50/50 coolant and it will probably say it contains Distilled Water
 
Joined
Jun 6, 2013
Messages
1,361
Location
sw ohio
The whole towns water is RO? That is amazing.
Yes it is. RO is very expensive to implement and consumes hugh amts of electricity. the drinking water supply must be contaminated with haz chems that require removal. RO is the ultimate process. Some ppl with young children install home RO units
 
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