Good to know. Maybe it would work, but I can’t recommend it to others. I personally still wouldn’t mix tap water into the cooling system unless I was desperate.

Agreed about the coolant and the brake fluid.

I agree distilled water is best, but if you flush out the coolant system every 2 years should not have a problem with city water mix it 50/50. I used tap water for 25 years on a DD pickup truck with cheapest coolant I could buy never had any issues. That pickup got a flush every 24 months I kept a maintenance schedule sheet in my glove box. When we pulled the engine for a rebuild at 220k entire cooling system was clean as an engine that was a few years old. The newer coolant claims it can go longer my new pickup I got in 2015 RAM 2500 Diesel says every 10 years or 150k I flush it every 3 years. Coolant is about time breaks down over time not so much how many miles. I learned my lesson with coolant when I was a teen let it go 5 years when I drained full of rust on a new car. Biggest things overlooked by car owners Coolant, and Brake fluid and both can bite you for letting it go too many years.

Do you have a source for that? Tap water contains minerals that can corrode the cooling system. I think most manufacturers use deionized water (which is even better for cooling systems than distilled water).