I agree with both peeps. My view. If I am on The side of the road, whatever clean water I can get will go in. Later I will flush it. Companies don't make coolant for no reason and in two different types. They have a reason. Straight water is only to save your ***. If running water is the thing you prefer then distilled because over time that **** is gonna scale up. Anyways back to original topic. Nice insides

 

don't worry you won't find me getting butthurt over what someone says on a forum. i can tell you that i don't need to go around and ask them because i'm not interested in opinions. i am only interested in proven scientific fact and that fact still remains. tap water is bad for your motor, period. just like buying a cheap radiator with a lifetime warranty makes no sense when you can buy a good mish or koto with a lifetime warranty for a little more. sure you pay a little more but the added benefit outweighs the cost (not to mention it looks so much better). same with using distilled water @ what like $5-6 to fill an empty coolant system a year? it's just a no brainer. so unless you are 100 miles from a store and really need to use what you got, it just does't make sense to use tap. next time you crack open a block check the water jackets and see if they're crusty. buildup in the radiator or the water passages is a sure sign of poor maintenance or bad water.

 

considering the cooling system is a closed system, you could run anything in there for emergency or short term purposes.
but here's a test - fill up a clear glass of tap water and then a clear glass of distilled. let it evaporate. if theres any residue left on the tap water glass, then that's what will build up eventually. if you flush it often, then it's not a big deal. but i've had to rebuild motors with massive amounts of build up in it and if you were to come to me with a motor to be rebuilt with that kind of build up, i'd tell you not gonna do it, and go solvent tank it first as well as replace the radiator.

 

by the way, i'm a huge hypocrite as i just filled up my miata with tap water. LOL. short term only though, i just wanted to test for leaks and actual cooling ability (new rad and hose setup).

 

Ive rebuilt many engines that has used tap water in the system. majority of them being diesel engines, and most of the diesel engines i can honestly say theyre crusted up big time, BUT only because they do travel for miles and miles and through months and months without routine maintenance and not to mention poor maintenance (bad mixture, more water than antifreeze). out of most gasoline engines ive rebuilt (maybe only total of 3 gasoline engines ive torn apart) not as much crusting up in the water jackets. once again these vehicles are poorly maintained, i work at an individual shop and we work on other companies' vehicles which means they dont care two ****s about theyre vehicle (most companies are like that). now with that being said i say tap water WILL cause an issue without proper routine maintenance and without correct mixture. But like ive stated before, tap water is fine as long as you have proper mixture and proper maintenance and it should be alright. So i am not totally against distilled water, for obvious reasons, it does the job very VERY well as you can see in houdnis post, but people please do not get all hyped up on tap water being absolutely horrible for your engine, just keep up your maintenance and make sure you have a good mixture and be sure to get a good flush once in awhile.

 

i guess for us car people, who actually flush and use the correct coolant, its not really a problem. its those that never ever even check, or just buy the orange or green coolant with tap water, and let that stuff just react with each other is when it gets bad. if possible, i try and use distilled, but i know ive been lazy and used some tap water with some filtering lol