Well, at least it is entertaining...
You make some good points about dirty cooling systems.
Since we are using pool equipment, I suggest you use your test kit to check the pH of your discharge water, to avoid killing plants & encounters with various agencies that want to make your life harder.
While you have the test kit out, may I suggest you perform a titration on the make-up water you plan to use for diluting your coolant. You are correct that a slightly acid coolant is better than one that is base.
FYI, straight distilled water will corrode all sorts of things - it is hard on pumps & plumbing in industry. Some dissolved solids are necessary to buffer the water. Distilled water is sometimes called "weld solvent" - you should see what it can do to a weld on a 304 stainless pipe.
De-Ionized water is even worse. As a friend said, "the fastest way to turn an aluminum radiator into a lawn sprinkler is to fill it with DI water" .
The big problem with some tap water is it is full of calcium carbonate & magnesium carbonate. Carbonates tend to precipitate out if the water goes over 100f for long periods of time. This causes a white scale buildup, and a loss of dissolved solids in the water.
If you have a water softener at your home, you are set. Water softeners use ion exchange to replace the calcium & magnesium with sodium or potassium. The net effect is markedly reduced scaling in a system because sodium and potassium carbonates are very soluble in water over a wide range of temperatures and pH; these chemicals do not come out of solution and if they did, they would redissolve.
So if you live someplace with hard water, there is a reason to buy the pre-mixed coolant which has the proper pH & dissolved solids to keep things in balance.
B.
