It's pretty easy to build your own rain barrels from plastic drums or trash
cans. Search online for “bottles” or “containers” to find an “open head”
plastic 55-gallon drum with a cover (about $60). Or find a used barrel by
talking to car wash managers (they buy soap and wax by the barrel). If you
can't find a container you like, buy a large, heavy-duty garbage can (about
$35) at a home center. All the other plumbing parts will add up
to about $40.
Place the drum near a downspout, drill a hole in the side near the bottom and
screw in a drain valve. That's an OK installation if you plan to run a soaker
hose to your garden. But if you want to use a wand or a spray nozzle, you'll
need to elevate the barrel on a stand for more water pressure. Water is heavy
(55 gallons weighs 440 lbs.), so use 4x4 treated lumber for the legs and secure
everything with construction screws or stainless steel lags. But don't place
the stand on soft ground. You could kill somebody if the rig toppled over. If
you have large gardens and want to store more water, double-size the stand and
add a second barrel.
Cut holes in the bottoms of the barrels with a 2-1/4-in. hole saw. Then screw
in a 2-in. male threaded electrical (gray PVC) conduit adapter (electrical
adapters aren't tapered like plumbing adapters, so you can tighten them down
all the way). Squirt a thin bead of silicone caulk around the opening and screw
on a threaded electrical PVC coupler to cinch the barrel between the two
fittings (see Figure A). Next, glue together sections of 2-in. PVC pipe, unions
(to make winter disassembly easier), reducers and valves. As long as you're at
it, install an overflow pipe so you can direct the excess where you want
it.
Finally, cut a hole in one of the covers and mount a screen to filter out
leaves and debris. Then just wait for the next big rain.
For complete instructions and more photos, visit...
http://www.familyhandyman.com/DIY-Projects/Green-Home/Saving-Water/how-to-build-a-rain-barrel