My water seems to be turned off, at the mains, perhaps once a year. Sometimes we get warning, sometimes we don't.
I do take precautions, filling washed empty 2 litre Pepsi Max bottles to the brim with water. Newer fills in a dark cupboard in the house for hot drinks / cooking / personal washing. Older fills in the garden shed, for washing etc... I also buy a few supermarket own brand bottled water in 2 litre bottles, with long expiry dates, for cold drinks.
The loo however would just get a squirt of Pine Toilet Cleanser, until water was restored. My main fear though, is the water or electricity going off part way through a soapy Power Shower !