Fill just one barrel with water and all 15 planters get watered as the plants need it.
Part II Leveling The Barrels (if your on a slope): https://youtu.be/WASyiqRA0fw
Part III Overflow Drain: https://youtu.be/65PMSwyfewo
How To Make A Global Barrel Part I: https://youtu.be/xewqTleDcIo
How To Make A Global Barrel Part II: https://youtu.be/9kKvQE3WQK8
The links for all the pieces you will need are below.
Grommet, Buna-N, MS 35489-75, Pk 10
http://www.grainger.com/product/3MRL5?gclid=CIa64_iN878CFYMF7AodVg
آی-ویدئو