Talking as to someone who did not have any running water for 10 days in 2007, and do not have a tank in my flat
It was horrendous without any watyer, sanitation was minimal, no pubs were open
. When the water runs out, what do you do......
Any one who has a cisterna, in my humble opinion, should collect every drop as they may need it (e.g after the fire on Rhodes last year).