Rain Harvesting - Bypass Overflow
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Underground Water Collection System
RAIN HARVESTING or RAIN CAPTURE is becoming increasingly popular for landscape irrigation due in part to recent improvements in drip irrigation technology. Darco manufactures both fiberglass and polyethylene underground rain water storage tanks.
A one inch rain on a 2000 square foot roof generates over 1000 gallons of free water. Arid western states such as New Mexico and Arizona support and promote Rain Harvesting and Drip Irrigation which returns moisture to the soil at slow absorbable rates with minimal evaporative loss.
Always design your storage system with a high volume bypass to divert excess rain water that can not be stored fast enough during a downpour. Also consider a tank overflow to release any excess water when the storage system is completely full. Both the bypass and overflow must be directed away from the tank and discharged where it will not cause erosion or lead to structural building damage. (See Illustration #1)
We do not recommend that you drink or bathe in rainwater unless it has been treated to your local Health Department standards. Rainwater should rightfully be used in a way that returns the moisture to the earth near the location where it fell, such as through outside landscape irrigation or a septic system leach field.
Roof water generally carries leaves, dust, bugs, bird excrement, and a variety of other undesirable elements into any rain capture storage system. Filtering the water before it fills the storage tank is desirable provided the filter has the capacity to process the rain as fast as it falls. This may be difficult to do in the case of a "cloud burst" event.
The second illustration depicts our Modular OcTank Rain Capture System with a simple filtration and clarifier module which includes an upstream bypass, strainer basket, and high capacity washable fabric filter.
Any clarifier or concrete interceptor tank will require some maintenance. Accumulated silt in the bottom must be removed every few years by vacuum truck.