Graham Wilson wrote:
The big risk must be that bacteria starts to breed in a simple water
filter cartridge.

I don't know about that - the incoming water is chlorinated to eliminate
bacteria, isn't it? You would only have this risk for water which had
sat in the filter for a long time before you used it. All the filters I
have seen advise you to run the water to waste for a minute or two if it
hasn't been used for a few days.

Neil