As suggested by someone else, when I had a question about water storage, I tried the Aqua-Tainer...7 gallons, food grade plastic etc, Got them at Wal-mart for $7.82 each. So far so good too. I don't have them stacked, but the label says I could. I drink a lot of water, so I'm rotating my stock frequently. They are guranteed not to crack of break for 5 years, and I'm thinking they might last quite a bit longer. I didn't wash them out initially either, just started using them and there's no bad taste.

Hope this helps.