Just like you are thinking about ! I take it right from my gutter's downspout. I keep a new plastic trash-can in the garage, and when the forecast is for rain, I place under the spout. Once its collected in the can, it gets run thru a coffee filter and stored in 5 gallon water jugs, the type used on office coolers. Then when I'm ready to use it, it gets run thru the filter one more time. I use a permanent type filter not the paper ones. Its easier, cheaper, and the water flows thru it better. You can get them at any "Dollar" store. One more thing..... unless you like lifting 42 pounds of water and plastic bottle on a regular basis, buy a cheap hand pump!!! The one in the above pictures cost me about $5.00 and is worth it's weight in gold. If you read thru my thread, you know how bad my back is. I've stored water for up to 8 months with no problem or algae growth, just don't let it sit in the sunlight.
"I was so much older then, I'm younger than that now"