Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Use filtered water from refrigerator water dispenser for coolant mix? 08 Expedition

Not sure of our water quality.
Important to consider? Or just use tap water?
Or buy already mixed coolant? Expen$ive?
Thank you.

I use distilled water when using a 50/50 coolant mix. I’m on city water but it does contain a fair bit of minerals that aren’t good for a car’s cooling system.
Certain cars like Hondas and Subarus like a very specific type of coolant. In fact, the generic FLAPS* coolant, when used on Hondas/Acuras, is referred to “Hondacide” because it does a job on your seals and waterpump. The manufacturer’s recommended stuff is more expensive because it tends to be premixed but you don’t change coolant /that/ often.
Make sure that your Expedition doesn’t require it.

*FLAPS = Friendly Local Automotive Parts Store.

What the refrigerator filter takes out makes the water look better and taste better, and possibly makes it slightly healthier for you. However, what the refrigerator filter takes out will make no difference to your car.

Clean distilled water mixed with the proper coolant is best.

Water from your air conditioner drain is good.

If your teapot gets a mineral buildup on the bottom, and you MUST use tap water, it would be good to boil it first so some of the minerals that precipitate out in your teapot do so before you put it in your car.

You are correct that the pre-mixed coolant is more expensive. I have never looked at it to see if they mix with distilled water.

It is really more important to use the proper coolant than to be concerned about the quality of the water. The biggest concern is not to use organic acid coolant (aka Dexcool) in a car that is not made to tolerate it.

Boiling your tap water will concentrate the minerals in it , not dilute them. That is why teakettles get a mineral buildup. Repeated boiling concentrates the minerals to the point wher all of them won’t stay disolved in the water.

I wouldn’t worry about tap water unless you have unusually bad minerals, or if you’re constantly having to add water to your cooling system. The deposits one sees in cooling systems are more often from poor maintainance, and are the result of corrosion.

I have a well and the water is not that good.

You shouldn’t drink it directly. So we have a few filters (Sediment, Water Softener to remove Magnesium, Bubbler to remove radon and an RO filter to remove arsenic.) Once the water goes through the RO filter…it’s about as pure as distilled.

Have your tap water tested before drinking it, if you haven’t already. Do not use it in the car. Minerals that are perfectly safe to drink can accumulate on your radiator and heater cores and cause premature failure, and acidic water that’s safe to drink can eat right through copper.

Water from the refridgerator coils crarys with it whatever dust and dirt (and perhaps mouse leftovers) has collected there. I would not assume anything.

Distilled water is about $1/gallon at the grocery store.

No matter how pure the water you use, it won’t stay pure very long…The inside of an engine is not a very “pure” place…Lets see, aluminum, cast iron, steel, lead, zinc, brass, plastic…Now lets pump scalding hot water through that, for YEARS…For extra fun lets connect a heavy ground cable over here, and an equally heavy positive battery cable over there…Now lets energize those cables over and over, every time you start the car, allowing hundreds of amps to flow through the coolant-filled engine block…

If you can drink it, you can use it in your radiator without worry…Be amazed that automotive cooling systems hold up as long as they do…

Around here, distilled water is 0.99 cents a gallon at Walmart or any other pharmacy. Not worth the dilemma IMHO.

But I have used tap water (car wasn’t really worth the 0.99 cents) without any apparent ill effect.

Caddyman has it correct – if you can drink it, you can use it in your car.

Since you have a water filter, then by all means use its output. Expect it to be marginally better than water straight from the tap, which ought to be quite acceptable anyway in nearly all cases.

Folks who insist on distilled water attain primarily peace of mind. No argument there.


...make sure it is a 50/50 mixture of engine coolant and distilled water.
Nowhich is cheaper? - One gallon of antifreeze plus one gallon of distilled water or - the premixed 50/50 antifreeze?
Motorcraft Premium Gold Engine Coolant (yellow-colored)
Does it even come in 50/50 premixed? Is there a suitable other brand?

Whenever I see “premium”, that means expen$ive.

I have never used premixed- here is why. After I drain the old coolant out, I always flush the system with a hose. When it first starts coming out with the flush, there is a lot of antifreeze and crud that wouldn’t drain.
I then add 50% of the stated coolant capacity and the rest water. I haven’t found a way to completely empty the system since they yook the petcocks (or later drain bolts) out of the engine block.


Nowhich is cheaper? - One gallon of antifreeze plus one gallon of distilled water or - the premixed 50/50 antifreeze?
I don't know what you pay for premixed coolant, regular coolant, or distilled water. You do though, so go to the store and do the math yourself. If you need to, bring a calculator, but most cell phones already have calculators installed.

You can use clean rainwater-Kevin

^ What? No block drains?
So how are we to clean the system?

I am also displeased that I can’t even check or drain the transmission fluid in this Expedition.

Filtered water is not the same as distilled.  The local water supply will determine if you need distilled water or not.


So how are we to clean the system?

Hopefully, you don’t need to clean the system. If you keep up with maintenance, all you should need to do is drain and refill the system.

You can clean the system by flushing it with clean water or by flushing it with a chemical flush purchased at the auto parts store. If you use chemical flush, you need to follow the directions on the bottle and make sure you flush it all out with water. If you use tap water to do the flush, you drain out as much as possible before filling the cooling system with coolant and/or distilled water.

The distilled water is cheaper, for sure. And unless you are draining and flushing out the old coolant, you really do need to use that Motorcraft coolant. This is an irritating, baffling thing the automakers are doing: using many different, potentially incompatible coolants. If you pull up the chart of Ford coolant recommendations, it’s amazing, looks like a rainbow of different coolants, depending on the model and year (and sometimes half-year).

1 gal of distilled water at the W-Mart is about $1.00 its cheaper to mix your own. I now use the “Globiel” in my own car. use to have Dexecool.

I too have used tap water in the past, but when my tap (well) water ate through my copper house pipes 10 years after the house was built I decided that if it could do that It was worth the extra $1 not to put it in my radiator. By the time I replumbed my house I had 16 patches in the plumbing.