Tag Archives: urban rainwater collection

Residential Rainwater Collection

How Can Urban Homes Benefit From Rainwater Collection?

RBRWC9241510Just like rural homeowners, urban households can benefit from rainwater collection. Unlike rural homes, most city homes have less space available for storage. Slim line water tanks and underground storage options allow those who live in an urban environment to collect, store, and use rainwater for a number of purposes.

You do not need a lot of capacity of storage for supplemental use of rainwater. For every inch of rainfall, a thousand square feet of surface will yield 623 gallons of water. A 2,000 square foot roof in Seattle will yield over 44,000 gallons of water annually. Even with only 3,000 gallons of storage, winter use can be as much as 100% or can be stored for summer irrigation demands. See chart below  – an average 2,000 square foot roof yields over 44, 000 gallons with only 3,000 gallons of storage capacity based on 120 gallons of daily demand.  (click the image for larger view)

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Rainwater is a clean source of water that needs very little treatment for irrigation, toilet flushing, or laundry facilities. Further treatment with UV disinfection allows for whole house demands including drinking water. With more demands on our water districts due to drought conditions, every drop helps. Why not benefit from this natural resource, rather than send it down the curbside drain?

Rainwater Catchment, Residential Rainwater Collection

Seattle Residents are Serious About Rainwater Collection

Underground Tank Construction3Seattle residents want their rainwater catchment systems to make a positive impact on the environment, as well as the quality of their water and rely on professionals to design and install their systems to meet these requirements.

An ARCSA accredited professional, ARCSA lifetime member, and ARCSA regional representative, RainBank’s founder and president Ken Blair has been designing and installing rainwater systems for residential potable usage since 2004.

Ken started his business in the San Juan Islands when it was the only county in the state that had an exception to the water rights law. 100 % of the systems RainBank installed in the San Juans were for potable usage because of salt water intrusion or low producing wells.

Ken moved operations to the Seattle area in 2010, shortly after the statewide change in the law allowing rainwater collection throughout the state, and has met the challenge of design and installation that works within the urban environment.  Click here for more info on Seattle rainwater.

slimline tanksWhole house usage requires enough storage to be a viable sustainable system. Buried tanks and slim line tanks make storage requirements possible in restricted areas.

A non potable system used for toilet flushing and laundry facility requiring little space for storage can be designed to supplement city water. As much as 49% mitigation of city water usage can be achieved when used with dual flush toilets and water saving washing machines.

For potable or non potable use, a rainwater catchment system must be safe, reliable, and easy to maintain for the customer. Rainwater collection system designs for household usage, potable and non potable are regulated by King County Health Department General Department Policies and Procedures for Rainwater Harvesting:  before permitting is awarded. Storage, conveyance, filtration and disinfection must be designed and installed in accordance with plumbing codes for public safety. “Rain water systems that are intended for potable uses must include plans prepared by a licensed professional engineer licensed to practice in Washington AND who is experienced in designing drinking water systems, a group B water system designer licensed by Public Health holding a valid certificate OR accreditation issued by American Water Catchment System Association.”

We all are aware of the commercial building boom in Seattle. With larger roof areas and increased demand on our centralized water systems, many projects are turning to rainwater harvesting to meet the new requirements of retention of runoff water on site. Irrigation, toilet flushing, and wash down systems are being designed with rainwater collection being the source of water as a practical use of this runoff.

RainBank Rainwater Systems meet these projects needs with the most experience in metal tank construction and consulting in design in the Seattle area.

Residential Rainwater Collection

Cement Cisterns Collect Urban Rainwater

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With limited space in urban areas, cement cisterns are being built beneath homes as a rainwater harvesting solution.

tank linerWith the new “Green Storm Water Infrastructure” or GSI mandate, Seattle based RainBank Rainwater Systems is seeing increased interest in rainwater collection.  But, with limited space on an urban building lot, the storage of rainwater in above ground tanks is not an option when required to mitigate thousands of gallons of roof runoff.

With many new residential construction projects building on small city lots, there is just not enough room for a rain garden. One way to solve this issue is with a cement vault, constructed beneath the house, which stores the captured rain water for potable use.

The average 2,000 square foot roof area will yield over 44,000 gallons of water.  However, a cement vault cistern needs special engineering and considerations. Water weighs approximately 8 lbs per gallon and 1 cubic foot equals approximately 8 gallons. Calculations of weight and sheer need to be engineered for Seattle’s seismic zone. Additional ventilation should be considered along with aeration.

waterproofing tankCement water tanks are not naturally waterproof; cracks in concrete can result years after construction. The use of a liner, whether spray on epoxy, or a poly bag will prevent groundwater from entering the water tank as well as improve water quality.