If you are like me, it is delouge or drought. We either get no rain, or it rains 1/2 inch plus which overflows my rain barrels. I have wanted to go to multiple on a couple downspouts, but the whole thing looked complicated or my wife thought it looked unslightly. Then I discovered the rain barrel siphon.

So easy I don't know why I did not think of it before:

5 ft, 1in PVC pipe
2 90 degree slip couplings
2 endcaps

1) cut into 2 x 2ft and 1 x 1ft.
2) fit together into U shape
3) fill with water and then cap both ends
4) insert into barrels and uncap underwater

Total at Lowes = $5.15

This siphon equalizes the water fast with no hassles. If you are concerned that it will not move the water fast enough in a downpour, I am sure you could do the same with a 1.5 or 2 in pipe.

I am even going to spray paint the siphon in the front to match barrels so it will look better to my wife. But this is an extremely easy way to hook-up multiple rain barrels, really you could connect several this way if you wanted.