We had a leftover downspout diverter from the Fiskars Rain Barrel http://www.rain-barrel.com/tuscanyspicegranite.html that we installed at the front door. I used this to supply water to the barrels.If ...
Here are the parts that I used and the price. This is for building the piping and valve assemblies to draw water out of the barrel. The parts needed for bringing the water into the barrel are handled separately in step 4. All of the following parts can be purchased at Home Depot.
2 2" DWV MIP Adapter - $0.90 each
2 2" DWV Street Elbow 90 degree Spigot x Hub - $2.01 each
1 2" PVC Pipe (2' section pre-cut) - $2.21
2 2" PVC Tee - $2.49 each
2 2" x 1-1/2" PVC Drain Waste Vent Flush Bushing - $0.86 each
2 1-1/2" x 3/4" PVC Schedule 40 Bushing Spigot x FIPT - $1.27 each
2 3/4" Short Galvanized Nipple - $0.98 each ** I chose not to use this but instead got the PVC schedule 80 (gray) equivalent from my local Ace Hardware for $0.79 to prevent as much metal in the design as possible.
2 3/4" PVC Ball Valve - $2.94 each
2 3/4" MPT x 3/4" MHT adapter - $3.53 each ** While my local Ace Hardware did have this piece in plastic for less, I chose to go with brass here to better withstand contact with the metal threads on my hoses.
1 can of PVC primer and cement - $6.96
NOTE: For a single barrel design you do not need the Tees or the PVC pipe. You have the option to change the 90 degree Street Elbow with the 45 degree Street Elbow to reduce the bend of an attached hose.