How to Build a Garden Ecobin.

Latest Update 3rd May 2016.

The Ecobin is a self watering garden bed large enough to grow one or two tomato sized plants.  They are made from cheap black polypropylene garbage bins, but the water tank and supply system transforms them into very sustainable veggie growing beds especially if the soil is kept biologically active with frequent applications of high quality organic compost.
The cheap black bin has been painted a light colour to lessen overheating in summer.  

The 50mm hole in the side of the bin was drilled 200mm above the bottom of the bin.  It lines up with the overflow pipe sticking horizontally out of the contraption on the right of the bin.

This contraption is the water tank filling system and its made of readily available components.
  • The blue fittings are all standard 50mm irrigation components.
  • The black tube is 50mm slotted, corrugated irrigation tube and distributes water quickly in the water tank without getting blocked by the Scoria in the tank.
  • The white rigid PVC pipes are regular household plumbing items.
  • The water level indicator (emerging from the top of the filler tube) is made from 6mm Tasmanian oak dowel, with a floatation device (table tennis ball) glued to the bottom.
A 35mm hole is drilled in the filler tube to allow water to overflow if the water tank is full.
The blue components are sealed with silicone to hold them in position and stop soil blocking the system.
The assembly fits neatly into the bin with the overflow pipe extending out through the 50mm hole in the bin wall.
The bin is filled with Scoria up to the level of the overflow pipe.  This 20mm particle size Scoria is used in all my Ecobeds because its light and leaves spaces between the particles to allow the water to occupy at least 50% of the tank's volume.  Its there to support the soil above, and will wick water up into the soil.  A layer of geo-fabric is placed on top of the Scoria to keep soil out of the water tank without interfering with this wicking effect.
Good quality organic soil is added up to 100 mm from the rim of the bin, and a layer of high quality homemade compost is applied to the soil.  Finally, the compost is covered with mulch to restrict water lost from evaporation.

The 10mm tube extension on the end of the garden hose reaches down to the bottom of the filler tube, so water doesn't splash out of the overflow pipe, when filling the tank.  The overflow pipe has a piece of shadecloth zip tied over its opening to keep pests like mosquitoes out of the water tank.