Rainwater harvesting overflow discharge location - methods
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Overflow Discharge Locations / Methods Advantages Disadvantages
Discharge to grade via gravity flow (most recommended
  • Simplest method to design, install and operate
  • Low probability of rainwater backing up the overflow drainage piping
  • If discharge location not preparedd properly, may cause soil erosion at site
  • May pose a nuisance/safety issue if discharging large volumes from big catchment surfaces.
  • Overflow drainage piping may freeze if large sections are above the frost penetration depth; ice may build up at the point of discharge if not designed properly.
Discharge to storm sewer via gravity flow
  • Ideal for below-ground tanks as storm-sewers are also located below grade.
  • Storm sewers are specifically designed to collect roof runoff and direct it to an apprpriate location off-site
  • Design must prevent backflow from storm sewer into rainwater tank.
  • Stormwater discharges can have negative environmental impacts on recieving water bodies
Discharge to soakaway pit via gravity flow
  • Permits the handling of stormwater on-site, which contributes to maintaining pre-development drainage regimes.
  • Environmantal benefits of groundwater discharge
  • In newer housing developments, an infiltration trench, serving multiple lots, may be built by the developer
  • Soakaway pits require extensive site work to design and install (high in cost)
  • Large rainfall events can exceed the infiltration capacity of the soil, requiring a separate overflow from the soakaway pit.
  • Suitable only for permeable soils

This page was last edited on 13 April 2020, at 19:15.

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