Most folks don’t think about water as a component of survival. But you should at least think of drinking water for a month or two. Store-bought water jugs are not really good for long storage. At a minimum I suggest keeping a few fivers from the hardware store. Buy an extra one when you get a chance. Don’t need to keep them full, just handy so you can fill them on short notice.
Then you have the “power out” rule. If a drunk takes out your line remember to not flush the terlet. Both the tank and your water heater are your first source of back-up water.
If your place is rural, think in terms of rigging your roof as a catchment. A metal or tile roof is a great choice for that. My Mom, long ago, rigged her house so’s she could catch a little rain water for her house plants. That can be a fakter depending on how “minerally” your domestic water might be.
Excellent ideas, many thanks! Your Mom sounds like she was a true gem, and as resourceful as they come.