Emergency Water Bank with Pump (65 gallons)

This isn't the perfect water storage solution, and it isn't meant for the long term. But it does one thing very well. When you know something is about to happen, like a big storm rolling in or a water main break in your area, it lets you store a lot of water fast. It's a 65-gallon liner that sits in your bathtub. You fill it from the tap, and the included pump lets you draw clean water out without contaminating the rest.

I keep a water pump of my own, though not this brand. As far as I know, this is the cheapest way there is to store a lot of water on short notice. Keep your long-term water in proper containers, and keep one of these folded in the linen closet for the day you get a warning.