Can you use deionised water in the cooling system?

Soldato
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I still cant find a definite answer. Can you use deionised or distilled water mixed with coolant in the cooling system?

Some seem to say ok, others say don't do it?
 
Soldato
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All the typical PC water cooling coolants you can find are mostly distilled or deionised water mixed with various things like glycol and corrosion inhibitors, dyes etc.

Distilled water would be best, but deionised is fine. You can run purely with water if you wish but you’ll need to maintain the loop a little more often as otherwise you may get biological growth. The main advantage of the various coolants over just water is added protection from corrosion and they usually contain biocides to help prevent fouling.

If you are just topping up your loop a little then, assuming you are using a typical PC coolant, a little deionised or distilled water will have negligible impact on your coolant’s additive ratio. Add too much and you may make the biocides/corrosion inhibitors less effective and dilute any dyes but that’s all really.

Edit, ignore all that rambling - I totally missed which sub forum this was!
 
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Soldato
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You can but you can also use tap water. The antifreeze is designed to be used with tap water and has the additives needed to stop things like galvanic corrosion and limescale. Depending on the car make there are different types of antifreeze though so make sure you use the right one so they don't react with each other.
 
Soldato
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You can on a temporarily basis. I wouldn’t advise it for any longer than a couple of months.

coolant is cheap enough, if you just need a top up then you can usually by a litre bottle for a couple of £.
 
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I can’t see it being an issue. Comma state on the bottle it’s suitable for the dilution of antifreeze.
 
Soldato
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I can’t see it being an issue. Comma state on the bottle it’s suitable for the dilution of antifreeze.

I didn't mean it would be an issue but its a waste of money. You can use tap water with antifreeze and there are no ill effects. Garages wont be putting deionised or distilled water in your car.
 
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