Really? It can be hard to pinpoint where the infection came from.
I boil water, cover, leave it overnight, then add it to the fermenter if needed. It does not have to be complicated.
I agree about the second part but beginners (doing partial boils) are more likely to underpitch cell counts with liquid yeast as they aren't making a decent starter.
cheers.
I understand that it would be hard to pinpoint the cause of the infection, so blaming on the water without looking into the other variables would not be a good way to rule it out. I'm just saying, that a lot of people top off with faucet water, including me, and have never had issues with infections, thus making me feel more confident that faucet water is ok to use.
With your method, unless you are vacuum sealing or pressure canning the container that you place the water into when you cool it, you are still risking infection. If there is any headspace at all in your container when cooling that hasn't been sanitized, there is a potential for some sort of bug to be present in it. I'm not saying it's a high risk, but there is a slight possibility.
Would I agree that the risk is greater when using straight faucet water? Yes, I would agree that the risk is much greater. But in an overall comparison, I don't think it's any more of a risk than when people dunk their arms in the fermenter to retrieve their fallen-in airlock grommet. If it were me, I wouldn't waste my time with making sure the faucet water is sanitized.
One thing that a lot of beginners should realize, is that yeast care and pitching is critical to a great quality beer. If they are using a liquid yeast, a starter should be made. If they are making a high gravity beer, the correct amount of yeast should be pitched. I'm not saying "If you don't do this, you are stoopid, lawls!!11", because I am guilty of not doing this as well. But, if good procedures are followed with yeast care, then I don't think using faucet water is a terrible idea.
I hope I don't sound like I'm being a dink, I know how sometimes the "tone of voice" can be perceived differently when reading something on the internet, I'm just trying to state my opinion. If everybody in history did things only one way, because one person thought that was the only way to do it, we would still be naked and living in caves.