So this was actually my second attempt at a rain barrel system. The first one was never completed as I couldn't get the drain to seal at the bottom of the barrel. This time I used the existing bung holes in the barrel (duh). The course threaded one fits a 2" pvc threaded adapter just perfectly. This rain collection is for over by the goats and chickens. It's placed behind the chicken coop so it has a 8x16 roof to drain into it.
For now it just has one 55 gallon barrel, but it was made modular so I can expand the platform and put on more barrels. I should be able to fit up to 7 barrels (around 385 Gallons) behind the coop. This should provide enough water spring through fall instead of hauling it (or a long hose) a 100' to where the house faucet is.
Click on any image below to view a larger (around 640x480 pixel) image. The last picture shows the system installed. The initial test - running a hose onto the roof worked fine for the 3" of water we put in the barrel. It's supposed to rain later tonight and the next two days! I'll try to update this after it rains! There is a hole in the middle of the gutter at this time so probably only get water from 1/2 the roof. I'll replace that gutter next dry weekend. Right now the overflow tube just flows out towards the goat area - eventually I'll need to put a better drainage tube to keep the erosion down. Also, if this works well, I'll run the output module around to the front of the coop for ease of use.
If this works well, I'll be creating a couple more. At least one for the end of the barn - possibly one on each end and one behind the workshop. We are hoping hopeing to put some garden plots behind the barn and use these collection barrels for that watering.