Actually, you can get a RO or RO/DI unit here on SWF, or shop around some for the best price/product.
An RO or RO/DI unit will remove all harmful chemicals, pesticides, metals, ect from your tap water. I personally use and prefer SpectraPure's systems. They are a little more expensive than the other companies that are out there, but If you'll look at all of the resteraunts and gas stations systems, they are SpectraPure.
As for storge, I am using a 55gal drum. It takes akot of room, but I always have water ready for those emergency situations.
I bought my 35gal per day system about six years ago for a little over $200, and it was worth every penny!