Why Do It

storage_reuse.jpgRainwater Storage and Reuse prevents stormwater pollution in several ways. It slows down roof runoff, which protects streams from erosion and reduces flooding. If you are in a combined sewer overflow (CSO) area, it reduces sewage discharges into streams and bays during heavy rains. Stored rainwater from cisterns can supply water for irrigation, and possibly some indoor uses.

In South Portland, storage and reuse is considered an option for Basic or Post-Construction Stormwater Management Plans.

See other Basic or Post-Construction Stormwater Management Plan options here.

Basic Features

A rainwater storage and reuse system includes a cistern connected to a gutter or downspout. The cistern should have a screen that keeps out insects and debris, along with a method of automatically draining enough volume in 24 to 48 hours after each storm so that the required stormwater volume from the next storm will be captured. A use for the water is an essential part of the system. A method for safely diverting flows which exceeds storage capacity is needed, as well. Cisterns are typically very heavy when full, so adequate structural support is essential. Filters or disinfection systems may be part of the reuse component.

Design and Installation

Given the complexity of Storage and Reuse systems for commercial installation a professional engineer and architect should be consulted on design considerations.  There are also numerous private businesses dedicated to providing these types of services which can provide engineering assistance.

Download detailed design specifications for Rainwater Storage and Reuse Systems.


Maintenance requirements for storage and reuse systems involve inspection at least twice a year and the repairing or replacement of appropriate components. Inspections and repairs should be done during dry parts of the year such as in summer. Having the option of completely draining the system for maintenance is highly recommended. If the system is being use for a Basic or Post-Construction Stormwater Management Plan, a legal entity must create and sign a maintenance agreement, consistent with the South Portland Code of Ordinances.