[krisoft]

> It’s not recommended to use straight tap water here, only filtered, due to bacteria which is harmless to older children/adults but could be a problem for a newborn.

I’m very currious about the filter you mention. How do you filter bacteria out in a household setting? How do you keep the filter itself clean and how do you QA your solution?

I find it likely that any filtering done by average people is more likely to add bacteria than to remove it. But maybe there is some magical method I don’t know about yet.

[cjrp]

To be clear, it's not my recommendation but the NHS' - https://www.nhs.uk/conditions/baby/weaning-and-feeding/drink...

The filters are things like this https://www.tommeetippee.com/en-gb/product/perfect-prep-repl...

[krisoft]

I read the linked NHS document multiple times and I can't see any reference to filtered water. They only talk about boiling the water. Where are you seeing that they recommend filtering?

[germinalphrase]

Why expect that a charcoal filter, changed at the recommended interval, would add more bacteria than it removes?

[krisoft]

Because of two reasons together: charcoal filters don’t remove bacteria[1][2], that is the reason why I don’t expect it to reduce bacterial count. And then any user error (less than pristine pitcher, filter not replaced at the recomended interval) would increase the count.

But there is also a different reasoning. A more philosophical, heuristic based one: The water where I live is treated by professionals with professional grade equipment. They also take regular samples and try to grow the bacteria to be able to tell if they are doing their job right or not. And the quality, at least where I live, is generally good. To improve something from good to excelent you often need to put in as much work as it was already put in to move it from mediocre to good. It is possible of course, but I would expect the process to be either energy intensive, or fiddly, or resource intensive, or require even more specialised equipment. Most likely all four at once. A simple, easy to use, and convenient filter doesn’t pass my sniff test. Like if it is that easy why wouldn’t the pros just do it at the water treatment facility?

Now of course this is just a heuristic, it can go wrong many different ways. And I admit I can be wrong of course. This is very far from my expertise. But this is how I was thinking about the question.

1: https://www.livestrong.com/article/193977-what-do-carbon-fil...

2: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC242697/