danglerb

When doing a normal 50/50 coolant refill I have been careful to only use the finest Walmart or grocery store brand of distilled water. How bad is it to use tap water?

Living in OC now, but when in Riverside it was possible to make a battery with tap water.

Avar928

Finest Walmart water. Sorry I just thought that was funny.

The advantage of distilled is that there are no impurities. Hard water will cause build up in the radiator more likely. Run distilled for the long run but I wouldn't think regular hose water for a flush or for a limited time will do harm. I flushed my coolant with regular hose water before replacing with G07.

The Fixer

Hey Mike, I don't think you should use tap, use the distilled.
Take care,-Matt

GregBBRD

I use distilled water, because I use expensive coolant and it seems like the water is a very small percentage of the overall cost.

However, since most of these cars are now over 25 years old and have not all been pampered by fanatics, it is highly likely that what you are removing came from the faucet.

martinss

There is no consistency in what is accepted as tap water in different locations and at different times of the year, so one cannot generalize. For example, some areas have very high iron or calcium levels, that other do not. Best to go with distilled. Compared to the cost of other 'parts' we buy, it is cheap...

Chalkboss

I work in a lab so easy to get DI. Check the hardness of your tap water. Hard water not good. I forget the values but you should be ok with numbers on the low range.

17prospective buyer

How "bad" it is to do this would deffinitely depend on locale more than anything, it's composition/analysis.

daveo90s4

I'm not sure that distilled water is correct. To be purist shouldn't one be using deionised water? Not that anyone does....

Chalkboss

I do... but it is overkill imo. Distilled is typically not as pure as DI but perfectly fine for engines.

dr bob

DI water is starved for ions and therefore just a bit corrosive. Distilled isn't as vicious.

Mike--

I don't know how hard the water is in your neighborhood. Here in sunny Glendale (45 miles north and west), we get some combination of Colorado River water, Owens Valley water, central valley water, and ground-well water. The stuff that comes across the desert in canals is concentrated by evaporation on the way. Groundwater here is only marginally better. The result? An average of 35-grain hardness in the samples I've looked at over the last ten years here. My OC water in the west county was marginally better with a higher percentage of well water, but still north of 25 grains hardness from the tap. In both places I added a water softener (cation resin bed with salt-water flush) to keep the bathroom clean. In Glendale I added a second cation resin bed tank just for car washing. It's essential in my opinion for dark-colored cars.

Now, what did you want to put in the radiator?

jeff spahn

So Dr. Bob what you are saying is when you turn on the faucet rocks come out?

dr bob

Yep. Without the softener, it's parts-per-part.

jon928se

Easiest way to make a preliminary assessment is to look in your hot water kettle (assuming it's say a year old and in regular use) If it still looks like new inisde then should be minimal problems. If it looks like the inside of a limestone cavern don't touch it with a barge pole.

jcorenman

35 grain? Yikes! Our well runs around 150 mg/L and I thought that was bad... And yes, we mix purified water with the coolant, and softener+DI cartridges for car washing.

Hilton

'muricans don't usually have kettles... something I've never got used to when visiting the in-laws. (heating a mug of water in the microwave is just wrong!)