So, I wrote an article a while back about finding water in the zombie apocalypse. I now realize that I forgot a great source: hot water heaters. There’s a hot water heater in every home in most advanced countries and it’s filled with fresh water! Opening it and getting that water out might pose a challenge, though.
As most people are aware, hot water heaters can fucking EXPLODE! As far as I know, this is only true if the heater is on and is compressing evaporated gases inside the unit (since water can’t be compressed). Once the grid is down for a bit, all the water heaters should be safe. In that interim time, water should be available from other sources.
If not, be very careful. There should be a pressure release valve on every hot water heater in the United States. I can’t speak for other countries, but I’d be surprised if safety regulations didn’t require them everywhere. Pull that pin and let all the pressure out before attempting to access the water inside. There should be a panel on the outside of the unit that you can remove and access the innards of the contraption. From there, you should be able to get to the water.
If not, just bash the bastard with a hammer till you get there.