Flushing Radiator with Tap Water

[pemdas]

This is something that I always questioned and wanted to read what others thougts are regarding flushing with tap water.

If you do a cooling system flush using tap water you will never get all of that water out of the system. Once you refill the system with a 50/50 mix coolant and distilled water, some of the tap water will still be circulating in the system. That tap water has chemicals and minerals. The minerals will end up causing problems and buildup in the radiator. Does this make any sense to anyone. Wouldn't adding distilled water to flush the system make more sense?

 

[d00df00d]

I've been wondering the same thing. I'll be watching this thread for informed answers.

I was under the impression that coolant was formulated to compensate for the presence of such chemicals and minerals, as similar stuff can build up over time in normal service. Given that, if I had to guess, I'd say it'd probably be fine to use tap water just for a flush as long as you plan on regular coolant change intervals -- say, every 2 years or so. Just my guess...

 

[ConfederateTyrant]

I would use the garden hose for an initial flush (when the coolant coming out is clear) and then I follow it up with 6 gallons of distilled water. That will dilute the tap water, to the point of very minimal, and in my opinion, nothing to worry about.

 

[JHZR2]

I wouldnt introduce it to the coolant, but if only doing the radiator, if you run the hose through with the valve open, you should be able to flush it pretty well. Then, after it all drains, unless you have VERY mineral-filled water, there wont be much of anything left in there, especially if your fill finally with distilled water.

In my opinion, if the system is maintained well enough, you likely dont need to put more than a gallon throug to keep things clean. That said, I usually just flush with a gallon or two of distilled water, so that everything stays constant and there isnt much mess. Distilled water is cheap enough...

JMH

 

[bdcardinal]

well considering that almost every shop ive worked at has used tap water in coolant, i wouldnt worry about it. also most coolant companies say their coolant can be used with tap water no problem.

i guess if youre really worried, let it sit with the block drains out overnight and fill with premix.

 

[kd5byb]

I don't think it's worth worrying about.

Yes, tap water has minerals and other stuff in it like chlorine and fluoride if you're on city water. If you've got very hard water, you'll have a lot of minerals in it - around 200 parts per million. (source = http://www.water-research.net/hardness.htm)

But, the coolant you add has chemicals in it to prevent those residual minerals in the water from doing any harm. Coolant isn't just for freeze-point depression and boil-point elevation, it has additives to prevent metal corrosion and scale build-up from dissolved minerals.

If it causes you to loose sleep, change your coolant out more frequently. This refreshes the anti-corrosion chemicals and ensures you won't have harm.

later,
b

 

[frank2009]

Great question! something i've womdered about too. Love this board!!

Anyway, as others have said, probably no big deal. The shop manual for my dodge neon recommended a flush gun for cooling system service. I'm sure that'd be hooked up to plain ol' tap water.

 

[pemdas]

Thanks to everyone for their replys. Lets expand on this.

The antifreezes of today I am sure provide excellent protection against mineral buildup from tap water in the radiator. Would it be possible for those minerals to become a problem as the antifreeze ages?
The reason why I bring this up is because I remember a cousin that had a Thunderbird. When I checked inside the radiator there was excessive white scale buildup in there to the point the radiator needed to be replaced.

1. Could mineral buildup be caused by a small amount of Tap water in the mix as the antifreeze ages?
2. Could mineral buildup be avoided if distilled water is used or are there additional factors that cause this?
3. Would it be a better insurance policy to simply flush with distilled water which would avoid this problem or would it not make a difference?

 

[Chris142]

We flush with tap water and then flush that out with deionized water. The water here is very hard and you don't want to be running it in your engine.

 

[Headnsouth]

Automobile manufacturers get the coolant in mass quantities, undiluted and use regular old tap water to make the correct mix for the application. I can’t see tap water being an issuethey've been doing it that way for forever.

 

[pemdas]

Originally Posted By: Headnsouth
Automobile manufacturers get the coolant in mass quantities, undiluted and use regular old tap water to make the correct mix for the application. I can’t see tap water being an issuethey've been doing it that way for forever.


This is what Peak antifreeze has to say about the tap water question.
http://www.peakantifreeze.com/faq.html#B

B. Can I mix ordinary tap water with antifreeze?
Yes, tap water is commonly used for mixing with antifreeze, however, deionized water or distilled water is preferred. Do not use water softened with salts to mix with antifreeze.

 

[XS650]

Originally Posted By: Headnsouth
Automobile manufacturers get the coolant in mass quantities, undiluted and use regular old tap water to make the correct mix for the application. I can’t see tap water being an issue they've been doing it that way for forever.


There's tap water, then there's tap water.

 

[Headnsouth]

Originally Posted By: XS650
Originally Posted By: Headnsouth
Automobile manufacturers get the coolant in mass quantities, undiluted and use regular old tap water to make the correct mix for the application. I can’t see tap water being an issue they've been doing it that way for forever.


There's tap water, then there's tap water.

Like what regular and regular regular?

Distilled is recommended but I doubt ever used by manufacturers.

 

[XS650]

There is tap water in the US that is almost mineral free, then there is water that is full of minerals.

I seriously doubt that a car manufacturer would use truly hard water in new car coolant.

 

[Headnsouth]

Originally Posted By: XS650
There is tap water in the US that is almost mineral free, then there is water that is full of minerals.

I seriously doubt that a car manufacturer would use truly hard water in new car coolant.

Most water that i've seen outside of Florida is pretty soft. Unless its wellwater. But I'm no expert.

 

[doitmyself]

Water quality varies tremendously across the U.S., so generalizations about using tap water should be carefully considered.

My well water will turn orange (honey color) sitting in a bucket for 15 minutes (iron reacting with oxygen, I'm told) and it's ph is about 8.0.

As mentioned above, softened water is not recommended - is city tap water softened?

5 to 10 years ago, I don't remember seeing water recommendations on coolant bottles. Now, nearly every manufacturer recommends/prefers the use of demineralized water and states so on the label. IMO, I tend to think that today's coolant formulations are more sensitive to water quality...just a hunch. And, it's also probably tied to the longer change intervals recommended now.

Those here who say that OEM uses tap water....do you know that they don't have DI tanks mounted in line? My small greenhouse DI tanks will treat 1,000+ gallons for about 8 cents a gallon (I need to check the figures).

So, unless one knows the quality of your tap water, why go against the manufacturer's recommendations? The service garages that you guys say use tap water don't really care what happens several years down the road. Distilled water is too cheap and as they say "is a no brainer".

Again, based on MY well water, which is very hard.

 

[Headnsouth]

I work for a major auto manu and we do not have DI tanks. Tap water and coolant. shhhh!

 

[DracoFelis]

Originally Posted By: pemdas
This is something that I always questioned and wanted to read what others thougts are regarding flushing with tap water.

If you do a cooling system flush using tap water you will never get all of that water out of the system. Once you refill the system with a 50/50 mix coolant and distilled water, some of the tap water will still be circulating in the system.

I really think it depends upon how "paranoid" you are. When I last had my radiator flushed, we took the following path:

1) The initial (and very complete/active) flush was with tap water (i.e. garden hose until the water was very clear), and then drain out as much of the water as possible.

2) We next closed/plugged the radiator drain, and filled the radiator with distilled water.

3) The car was next run briefly (on the water mix), to mix the remaining tap water with the distilled water (thereby diluting the tap water minerals with the distilled water).

4) Again, drain out as much water as possible. Because of the mixing in step 3, much of the minerals in the system should drain out along with the water (leaving the water that remains in the system with a much lower mineral content then before steps 2 and 3).

5) Repeat steps 2-4 a couple more times (i.e. a total of 3 drains/fills with distilled water). Each additional time filling/mixing/draining should again dilute any remaining mineral content in the coolant system. By the time you are done with 3 fill/mix/drain cycles (with distilled water), you should be left with only a very small fraction of the mineral content left by the initial tap water.

6) Again close up the radiator drain, and do the final fill with concentrate and distilled water. This wasn't exactly a 50/50 mix, because we had to factor in the water still "trapped" in the system (so we went a little heavy on the concentrate). However, that "trapped water" should have been mostly distilled water at that point (due to the tap water dilution steps previously done).

Mind you, that's probably a lot more paranoid than I needed to be, especially since antifreeze really is designed to fight mineral buildup. However, it also seemed silly to me, to let a lot of minerals go into the system after a radiator flush, when there were reasonably easy ways to avoid it. The way I figure it, the more minerals you introduce into your coolant system, the harder time any antifreeze will have in keeping down corrosion. So at the very least, keeping the minerals (from hard tap water) down after a complete flush can't hurt, and it might even help the antifreeze last longer (and maybe even help the radiator last longer)...

 

[oilboy123]

Well as you have seen in the news tap water has lots of prescription drugs, hormones etc in it as well.

I normally flush a couple of gallons of distilled water that I make with a distiller I got from my Grandfather years back.

 

[wagsg]

I was planning on this approach... what do you think?

Drain and flush with tap water until clear.
Drain and flush with 50/50 pre-mix until proper color is achieved (or as close as I can determine visually).
Drain and fill with 50/50 pre-mix.

I would run the vehicle to circulate fluid in each step.

Shouldn't this get most, if not all, water minerals out and achieve an almost perfect 50/50 mix? This will a first time diy coolant change for me.