Cut a length of ⅜-inch-diameter irrigation tubing and bend it into a ring that fits the bottom of the barrel. Join the ends with a T-fitting, and attach the remaining tubing to the T's third leg. Using a 3/16-inch bit, drill a series of holes into the top of the ring about 1 inch apart; they let air bubble up, encouraging the growth of beneficial bacteria and reducing odors.
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Drill (or drill/driver)
⅜-inch spade bit
3/16 drill bit
Pump sprayer (for applying the compost tea)