I can see maybe trying tap water if you have more than enough rad space and aren't having a cooling issue, the tap water won't get hot enough to form steam and leave trace mineral deposit as fast. I mean you might be one of the lucky ones that your municipality does a great job treating water and you only have some bacteria and chlorine in your tap water, but I have hard water (see mineral rich). And minerals like to deposit themselves whenever they can, ordinarily distilled water can be had for so little that it's a small investment for piece of mind.
No lol I have very hard water, I get calcium deposits on the shower.. And my other Hobby is fish tanks, I have 9 tanks in my house my biggest is a 100g corner tank with discus.. I also keep fish that need low ph and others that need high PH.. Our water here is very high in PH somewhere between 7.8-8.2 most of the east coast is like that.. So trust me lol I know how bad the water is here. As for bacteria.. I don't think there is bacteria in the water with the Chloramine they use lol.. We have Chloramines in the water which kills bacteria and how I know that is because testing the water with my kits for my fish tanks, shows there is about .5 to 1.0PPM of ammonia in the water, but it isn't actually real ammonia from decaying matter its Chloramine which is a form of Chlorine and Ammonia.
I just don't care to go to the store to buy distilled water, I know its cheap I work on cars as another hobby, ive changed countless radiators and done work to the cooling systems on many cars and I always use 100% Antifreeze with Distilled water because its cheaper then the premade 50/50.
But im telling you that I haven't had any issues as far as deposites in my radiator... Also if you are worried about deposites you do realize that having dissimilar metals (aluminum or brass radiator and a copper waterblock with brass fittings for example) in a cooling loop also causes the metals to break down quicker and can clog up a cooling system, it can break down the metals and also it even creates a small electrical charge in the system which breaks down the metals even more. If you don't believe me get a multimeter out and measure the cooling system in your car .. Unless your car is brand new I garuntee you will have a small electrical charge in the coolant.. Why do you think they put antifreeze in a car ?
It isn't just to keep you engine block from blowing up in the winter, they have additives in it like sodium and so forth which keeps the metal from breaking down.. If you just use pure distilled water the aluminum radiator and heads and what not in the system breaks down and causes mineral like deposites in the system.. Have you ever opened a cooling reservoir on a older car and seen deposits on the bottom of it ? That's because the coolant wasn't changed enough.. Antifreeze breaks down over time and its protection properties no longer work and so the cooling system breaks down.
If you guys want to be completetly anal about the water cooling system on a computer then I suggest you use a coolant for automobiles like water wetter or something similar.
They also sell coolant flushes, I could easily spend $15 on one and flush my cooling system in my computer if I was that worried about mineral deposits, also give it a good blow with my air compressor.
As for the OP, what kind of pump will you be using for 3 radiators and 2 waterblocks ? I hope its a strong pump
