Rainwater harvesting overflow discharge location - methods

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