Category Archives: Rainwater Harvesting Education

Rainwater Harvesting Education

Estimating Water Usage for a Rainwater Collection System

Rainwater Collection TanksIn order to establish usage for a rainwater collection system annual, monthly, and daily rainfall amounts,  along with water usage demands need to be taken into consideration.

Current water use is informative to help with sizing a system, but future demands should be considered as well. Growing family, guests, possible resale of the house should be accounted for. The system should be designed and built with upgrades for the future in mind, allowing for the system to supply what the future may hold.

Possible drought or longer periods of dry season should also be considered when designing or building a system. Incorporating back up water supplies into a system can be as easy as hauled water, or drawing from a well, community or city water system and should be an available option for those times. Residential rainwater systems in the city are often limited in space for storage, leaving the volume of the cisterns inadequate for year round use. Having the ability to switch to this alternate source can be a necessity in design. However, a more rural environment lends itself to larger storage capacities.

Water demand is an important part of design and the American Water Works Association (AWWA) has conducted a study of various fixtures and appliances. Knowing these demands will help estimate usage and assist the designer to adapt the design accordingly. Single flush toilets use 1.28 gal/ flush, dual flush toilets 1.0 gal/ flush for liquids and 1.28 gal/ flush for solid. Average use is 6 flushes per person, per day. Low use fixtures such as shower heads, faucets, cloths washer (front loading) are recommended for the overall design of the house and can be found in publications from manufacturers. 

Outdoor demand should be limited as much as possible. Drought tolerant plantings, drip irrigation, and general conservation will  help limit outdoor usage.

For specific irrigation needs, Evapotranspiration (ET) is the measurement of amount of water in inches that is needed to grow plants. All plants have a different watering requirements, also being affected by temperature, wind, humidity, and sunlight. A state climatologist can be contacted to attain an ET standard reference for your area. Careful consideration of outdoor use must be given if irrigation is part of the RWC design. An average city lot can use as much as 1,800 gallons of water for watering a lawn.

In order to get the best performance from your rainwater collection system, indoor and outdoor demands must be carefully calculated using best storage capacities, surplus and defect, level of storage, daily, monthly, and annual  use/demand for the entire year. Simply calculating the average annual rainfall amounts will not produce the end goal of a well designed RWC system. It is best to determine average potential of collection and use. Determine average daily, monthly, and annual rainfall amounts. Calculate collection area, and determine runoff. Identify highs and lows of rainfall amounts and demands. Determine those months of low amounts of rainfall along with the carryovers from months prior. Certainly, identify those months of zero rainfall.

Know your consumption of current and future use. Use water efficient fixtures and practice conservation. Understand that during those times of low amounts of rainfall, you may need to “tighten the belt a bit” or switch to the alternate source. Determine your desires and demands during the planning stage by doing so your system will produce the results you are looking for.

Rainwater Harvesting Education

Rainwater Collection and Quality of Life

Sierra Leone Africa School_RainBankLLCThe United Nations Environment Programme (UNEP) mission is to “provide leadership and encourage partnership in caring for the environment by inspiring, informing, and enabling nations and peoples to improve their quality of life without compromising that of future generations.”

UNEP was created in 1972 by the United Nations General Assembly for a wide range of environmental concerns and strategies, including Rainwater Harvesting and Utilization. A recent newsletter,  “An Environmentally Sound Approach for Sustainable Urban Water Management: An Introductory Guide for decision makers, cites nations around the world that are currently practicing rainwater collection as a source of water.

Examples are Singapore – with limited land resources and rising demands for water – has done a recent study of urban residential with conclusion of 4% savings from $1.17 per cubic meter to $.96 per cubic meter.  A non potable application at the Changi Airport accounts for a 28 – 30% savings.

Tokyo, Japan rainwater harvesting and utilization is promoted to mitigate water shortages, control floods, and secure water for emergencies.

About 750 private and public buildings in Tokyo have introduced rainwater collection and it is now flourishing in private and public sector.

Berlin, Germany rainwater utilization was introduced in 1998 as part of large scale urban development to control flooding and save city water. Germany is a leader in rainwater collection technology. Many products used in the United States come from Germany.

China has seventeen provinces that have adopted rainwater collection on a large scale with 5.6 million tanks supplying drinking water for 15 million people.

Of course, Africa is experiencing expansion of rainwater collection systems throughout the continent with the help of many NGOs in Kenya, Sierra Leone, Mozambique and many others.

Other countries  such as Australia, Philippines, Indonesia, Canada, and more are recognizing sustainable solutions to the worldwide need for a clean reliable source of water.

Rainwater Harvesting Education

Rainwater Collection is Catching On

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SeaScoutBase_Galveston_RainBank_projectBoth commercial and residential rainwater collection customers are expressing more interest than ever before, which is a large part of the reason that RainBank Rainwater Systems has seen a 50% bump in growth over the last year.

Architectural  and engineering firms are including rainwater collection systems in their designs. Cities, and counties throughout the state are beginning to understand the connection between stormwater management and rainwater collection.

Developers are saving money on large water bills with rainwater collection, while complying with he “Green Storm water Infrastructure” (GSI). Green building and low impact development are becoming more popular with the general public.  Residential customers, new construction and retrofits are recognizing the long-term cost savings, water quality, and security of a more decentralized water system. As a whole, the public is becoming more environmentally aware of our environmental impact and are finding ways to make that impact positive.

County and City planners, building departments, and health departments need to have the tools to make proper choices of acceptance, promotion, code and permitting of rainwater collection systems. RainBank’s president, Ken Blair is the American Rainwater Catchment Systems Association’s (ARCSA) Northwest regional representative and can schedule an ARCSA workshop for those civil departments, engineering and architectural firms this summer in Seattle. Interested parties please contact Ken using the contact form, or directly at Ken at RainBank dot info.