Capture and Reuse
Capture and reuse practices are designed to intercept and store runoff from impervious surfaces, such as rooftops, reducing volume and overall water quality impairment. The stormwater is contained and reused for irrigation but can also be used to supplement gray water usage. Typically rain barrels or cisterns are the vessels of choice for storing runoff for reuse. Underground cisterns can be designed to allow for seeping release into the substrate to recharge groundwater.
Rain barrels are designed to intercept and store runoff from rooftops to allow for reuse, typically for irrigation. The Department of Environmental Conservation recommends double rain barrels or cistern use, as these are able to store a larger amount of water, increasing their value both as a water quality practice and at times when greater storage is necessary and water is less readily available.
Design guidance for double rain barrels
- Rain barrels should be installed near collection point on the building
- Water should be used or drained between storm events
- Downspouts should be piped directly into the rain barrel through a screen to eliminate debris and prevent insect access
- The overflow outlet should be three inches below the top of the rain barrel and should connect to the next barrel; the overflow from the second barrel should be directed to an area to infiltrate
- Drain rock or a splash block should be positioned at the overflow outlet, similar to a downspout disconnection
Standard barrel size = 24”wide X 36” tall and holds 50 gallons
• Drain before a major storm.
• Drain before winter.
• Clean roof surfaces and gutters of animal droppings and leaves.
• Check the rain barrel(s) at least once a year for possible leaks.
• Remove deposits from the bottom of the tank as necessary.
A cistern is a container or tank that has greater storage capacity than a rain barrel. Cisterns may be comprised of fiberglass, brick, concrete, plastic or wood and can be located above or below ground. A cistern can range in size from 200 gallons to upwards of 10,000 gallons. Typically cisterns are used to supplement gray water and irrigation needs.
There are three main types of cisterns: above ground, partially buried, and underground. Generally, all types include the following components:
- Secure and solid cover
- Screen at entrance to prevent insects from entering
- Coarse inlet filter with clean out valve
- Overflow pipe
- Manhole, sump, and drain to facilitate cleaning
- Water use spigot
Other features may include:
- Water level indicator
- Sediment trap, tipping bucket or other “foul flush” mechanisms
- Tank lock
- Pump, if below ground
Design Guidance for Cisterns
Cistern volume is a function of roof area, precipitation required to fill the cistern, and anticipated use. In order to calculate the amount of runoff to be stored in a cistern and provide overflow for exceptional amounts of rainfall, use the following equation:
Alternative design considerations
- Concrete in-ground, cast-in-place cistern walls are recommended to be at least 6 inches thick
- Place above ground cisterns in open spaces to aid in maintenance and cleaning. Specifically, access to each cistern compartment should be provided through a removable surface plate
- Site cisterns in close proximity to buildings for roof runoff collection or near the area where the gathered water will be used most
- Size, material, holding capacity, and flow for above ground cisterns should be assessed by a site designer
* Above ground cisterns can be used with an irrigation system for outside use and non-potable functions. All water should be filtered prior to use to remove any solids.
- Clean roof surfaces and gutters of animal droppings and leaves
- Check the cistern at least once a year for possible leaks
- Remove deposits from the bottom of the tank as necessary
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