Experience has shown that ordinary tap water and some propriety windscreen wash products do not mix well. In my case it developed a cats pee smell and produced a black sludge in the reservoir.
I now use di ionised water and Autoglym and have not had a repeat. I know, some do not like diionised water but I have had no problems with this mix. Incidentally, the reservoir/jets did not freeze despite being down to -6 c.
De-Ionized water is fine with plastic, but not so good if you have any copper based alloys 'yellow metal' in the system (brass, bronze etc.) My wife rarely uses her windscreen washers and the fluid in the system gets a bad smell, and the screen gets smeary (I know how much is required to top it up as only I do it, she says she does not use it because it smells bad, I tell her if she used washers more often then fluid would not start to ferment and get the bad smell, but logic has never worked with a female). I have completely emptied her Jazz bottle a few times and refilled it with fresh so it smells nice, but she is not about to change her habits.
I use the same stuff but have to fill mine up every couple of weeks and it smells fine, if I use concentrated I only use tap water, but normally in winter I do get ready mixed so I am sure concentration is correct to stop it freezing.