When they returned, they decided to take unused 50-gallon plastic barrels from the waterworks, pipe them together, and fill them with pebbles and aquatic plants in order to test a multi-stage filter system.
回馬祖雙方討論後，決定以自來水廠閒置的 50 加侖塑膠桶為材料，在桶底鑽洞，以虹吸方式將水管串連起來，桶中放置小石頭、水生植物，藉高低落差來實驗「多層過濾」的效果。