BTW, this is classified as 'green' because my wife exclusively uses the water for the two 8x12 ft. gardens we have in our yard. We never water with a hose.
[Update 1 May 2010] We had a storm last night and got 3/8th of an inch of rain. When I looked this morning, the second barrel was full and was slightly overflowing down the sides. I just wanted to make sure that there was no problem with the pipe transferring the water from the first barrel to the second. In fact, despite the fact that the rain had stopped, water was still dripping from the downspout into the first barrel. The same amount of dripping was falling into the second one.
Step 1: Materials needed
-- 2 rain barrels (preferably PVC used by the food industry)
-- Length of 1/2 inch PVC pipe
-- 2 PVC connectors for 1/2 inch PVC pipe (threaded male end on one side and the other side smooth female)
-- 1 extension connector that is female threaded on each end
-- 1 right angle connector that is female smooth on each end
-- small container of PVC cement (optional)
-- Bricks to elevate the first barrel
13/16 inch drill bit
I paid $30 each for the used rain barrels at a local Indianapolis company. They come with with a cover that has both a larger and a smaller filler holes with threaded caps.
The PVC materials cost less than $5.