We use a filter for our household water, and have reusable steel bottles which we fill at home and take with us.
This page outlines several of the reasons we filter instead of buying disposable bottles:
link
If we had water that couldn't be made safe by filtration, I'm sure we'd use bottled water. If it was a long-term situation, we'd probably look into a service that provides water cooler bottles, and then picks them up for reuse after they're empty.