kettle water is fine. and it doesn't have to boil for any period of time, once anything goes over 65 degrees (and boiling is over 100) bacteria are killed.
and don't forget, most people are on treated scheme water too. (i live rural and have a windmill but our water is fine).
also, do you bath your babies? then they probably drink a few good mouthfuls during it and you don't even notice. so don't worry too much......
i've used kettle non-scheme (underground aquifer) water for both my babies and never had a problem. i don't even sterilise bottles as the hospitals say not to now.