All those tanks seem excessively expensive. Even the big ones are around $1.00 a gallon and the small ones (15 gallon) are several $ per gallon. You can buy bottled water at the grocery store--FULL bottles-- for $1 a gallon or so. To store 30 gallons I'd just use bottled water or 7 gallon stackable jugs (about $12 each) if I wanted to be a little fancier. For cheap storage of larger quantities I'd think of PVC garbage cans (maybe 15 bucks at the hardware store for a 33 gallon can?) lined with polyethelene bags, or even a kiddie swimming pool ($100 for a 15 ft diameter, 3.5 foot deep one, about 3000 gallons) if you have the space for it.

I wish there was such a thing as cheap desalination devices and I'm not sure why they don't exist. I'm about a mile from the ocean which means I have infinite amounts of undrinkable salt water available. A Pur 35 lifeboat-type desalinator (hand pumped, 4.5 liter/hour) is about $800 on ebay and I play with the idea sometimes, but it's too much cash for me to spend on something like that, plus it needs maintenance (annual biocide treatment) even if not used. If I won the lottery I might consider a 12 volt unit (26 liters/hour, $2500) with the idea of powering it from a portable generator or a car.