Rain Water Harvesting in Oatley

Jim Vickery , OFF member and retired Environmental Engineer, spoke on this topic at the 27th Oct meeting. Jim is determined to capture as much life- giving rain falling on his roof as possible by storing it in water tanks around his home. This reduces his reliance on town water supply and the erosive impact of excess storm water on our local streams. He provided guidelines and graphs showing the relationship between tank size and roof area based on rainfall records. In drier times, the Reliable Draw[water drawn every day without emptying tank ] is between Average Summer and Dry Winter levels shown in this chart. It is a useful guide relating storage volume and roof catchment area. A 2000L tank provides 50 100 L/day [if catchment is 100 sqm or more], sufficient to supply a
toilet in a small household and some water for the garden. A 6000L tank needs at least 200 sqm of catchment to supply water to a washing machine, toilet, and garden. Techniques for the collection, storage and delivery of rainwater were reviewed along
with uses for the water that overflows the tank. Jim runs his excess water into a swale in his backyard providing a bog that can recharge the water table. Running excess into a pond is another excellent method of harvesting rain water.
Rainwater tank installation guidelines:
  • Determine your daily need for rainwater.
  • Determine the size of your available roof catchment area.
  • A 2000 L tank will provide 50 to 100 L/day from a 100 sq m or larger roof.
  • A 6000 L tank or larger is necessary for supplying a washing machine or something similar. If the roof catchment area is greater than 200 sq m then the tank is less likely to empty out during dry periods .



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