Thank you for providing some sources. However I do not think they really make a strong point on explaining why tap water would be inadequate for cleaning PCBs on a hobbyist's scale:
First you provide two links on water quality and corrosive properties of tap water.
Yes, I know the complexion of tap water differs greatly regarding both mineral content and amount of small particles depending on factors like origin, treatment and plumbing. I also know water is always corrosive. Sea water is corrosive, rain water is corrosive, tap water is corrosive, distilled water is corrosive and de-ionised water is also corrosive. Still my claim is: When submerging PCBs in any kind of water that you would expect to come out of the tap in the first world for short periods of time this is negligible. At room temperature those processes are very slow. Constant exposure to air humidity over decades does a much better job at corroding metal on PCBs than a few minutes of tap water rinsing. Destilled water will likely cause less corrosion on PCBs, but is that difference relevant in our application? Both copper and tin (which together with gold make up the vast majority of exposed metals on PCBs) form a protective oxide layer on their surfaces that very effectively hinders further corrosion. I have never seen any proof there's a relevant difference regarding corrosion when cleaning PCBs with tap water vs. destilled water. Even chemists told me it probably doesn't matter.
The next articles are focussed on adequacy of (tap) water in cleaning PCBs. Though they do not really elaborate either, mostly stating that tap water will leave something on the PCB after drying from evaporation (ok, but what and what effect does it have/why is it bad?) and should not be used. I am actually interested in finding out what actual problems might arise from the (definately existent and from my pov completely irrelevant) amounts of minerals that might deposit on a PCB after thoroughly rinsing it with tap water. Both articles are not really interested in the effects of corrosion from submerging the PCBs in water which leads me to believe they also believe the effect is irrelevant at tap water ion levels.
The first article you present mostly deals with a lagre scale production point of view: Will residuals from various cleaning/rinsing solutions hamper further production steps? (The article gives drag in from alkaline cleaning agents contaminating an acid copper plating bath as an example.) Will the solution clean the PCB quickly so production can move quick? Will the solution dry quickly so production can move quick? All those questions do not apply to us hobbyists cleaning PCBs on a small scale.
My experience is identical to what's quoted in your second article:
We have been reworking circuit boards for the past 30 years. After solder touch-up we remove flux residues with ordinary alcohol, then clean with soap and water. We then dry each assembly with a blower. We have never encountered issues with microprocessors.
Btw. in the first response to that question the same article/discussion states distilled water wasn't good enough either.
In terms of precision cleaning, neither tap water nor distilled water are sufficiently pure to handle the job as both are contaminated, to greater or lesser degrees, with minerals and organics. So if you want to use water, you must jump to DI-water.
And I really think we can agree that as hobbyists we can safely disregard that position.
The second article/expert panel discussion also talks about process speed and reusability of water and besides that mostly focusses on wether water is sufficient to remove production residue like flux. Again this article/discussion is from an industrial pov. As hobbyists we're mostly dealing with dust and small amounts of organic fats/oils stuck on PCBs. Those can easily be removed with tap water and dish soap. With a good rinse the dish soap is removed as well. Blow it off with a compressor and you're golden. The amount of water and work used here would be totally unacceptable in production scale but for some dude tinkering with electronics it's not much of a problem.
The third article does little to enlighten on why destilled water is to be preferred when cleaning PCBs on a hobbyist's scale. Again my assumption and experience is: Corrosion on materials regularly found on PCBs from a few minutes of exposure to tab water will not be significantly different from the same amount of exposure to destilled water.
Meanwhile, distilled water has no contaminants or ions that cause damage.
Is plainly wrong. De-ionisied water contains no ions. Destilled water still has lots of them left. De-ionised water will very quickly solve ions from any metal it comes into contact with, again becoming regular conductive water capable of acting as an electrolyte.
The video you posted can safely be disregarded as an uneducated esoteric's approach to determining water quality. She actually scrubbed her water heater for residue that has come out of solution after heating and thinks it would have harmed her in any way because now she can see it. Again yes, there's more ions in tap water than destilled water, no argument. But does it matter?
I guess you can see how my serious question boils down to what actual difference there is when exposing PCBs to regular tap water vs. destilled water over a few minutes and how this difference will affect behaviour of electronics after drying.
And thank you from removing that part about me making intentionally bad posts here. I'm not trolling, I'm interested in finding out if there's any truth to the much heard saying of "only use destilled water for cleaning electronics" because I like to know if and how I'm doing something wrong as long as I actually am.
I think we're all friends here and we're all in the same boat. 😎