I take it you live in a area where you get summer rains? You should probably filter the water going in with 1/4 or 1/8 mesh wire screen. Is the top open so you can dip it out into a bucket and how big is your garden...
Thanks for your help.
Yes I am in Florida...we get a lot of rain.
My garden consists of several beds that are now in Garden bins, hanging pots and 4x4 raised beds. I have drip lines going to each that currently comes off tap water and I want to switch to rain water.
I was thinking I would try to replicate something like this as far as a barrel goes:
http://www.composters.com/rain-barrels/the-rain-catcher-rain-barrel——54-gal_160_10.php