Collection of Roof Runoff: Resource Conservation and Environmental Benefits

Objective

For selected private homes, collect detailed data on (a) household water consumption patterns, and (b) potentially collectable rainwater runoff from the same dwelling. Use the results to propose a system for cost-effective collection, storage, and use of rainwater in such homes.

Background

The water resources of the US northeast currently are more than sufficient for the demands people impose upon them. Fresh water supplies typically are stored in reservoirs or rivers and/or in the subsurface environment (artesian unconfined aquifers).  Households typically consume water in a single-use pattern, with the primary uses being drinking, cooking, washing, flushing, cleaning (house, car, etc.), watering lawns and gardens, etc. In the case of households connected to a public water supply system, the water bills include fees allocated to water purification—the complex physical and chemical processing of fresh water to remove contaminants.  The purity of water distributed to homes is defined by the USEPA under the Clean Water Act and the Surface Water and Ground Water Treatment Rules and their occasional amendments, and are known as the National Primary Drinking Water Standards (NPDWS).  For single-family homes, daily water consumption ranges from 150 to 300 gallons per capita, all of it purified to meet NPDWS standards. The only alternative water source that meets the NPDWS standard is rainwater.

Water conservation has been implemented in many different ways, e.g., modifying fixtures to reduce water wastage; installing smaller water tanks for flushing toilets; using reclaimed wastewater for washing cars and watering lawns. These methods focus on ways to conserve treat fresh water after it has been piped into a dwelling. This project will take a somewhat different tack, by focusing on the alternative of including rainwater in the mass balance of water demand for each individual home. While the concept can be expanded to apartment buildings, this project will focus on private dwellings.

Suggested Approaches

(i)  Selection of representative homes and rainwater data collection:  Select representative homes within or outside New York City that can be classified as one-family or two-family homes. For the selected homes, (a) collect detailed water consumption data via close monitoring of the water meter over a prolonged time period; and (b) equip all rain gutters in the vicinity with equipment that will allow measurement of all rainwater that reaches the roof or concrete surfaces adjoining the house. Ideally, the study should extend for 12 months, to capture evidence of seasonal variation.

(ii)  Analysis of results: Use the collected data to comparatively analyze the water deriving from the public water supply system with the quantity of rainwater runoff from the same premises.

(iii) Proposal for rainwater collection system: Propose a system for efficiently collecting, storing, and using rainwater in the context of one and two-family homes. The system should take into account possibilities for underground storage, and options for in-house distribution. Provide an economic analysis of the proposed system.