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

With 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.

Cement 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.

Ken Blair

President at RainBank Rainwater Systems

A rainwater collection systems designer and consultant, Ken has designed and installed residential and commercial systems, primarily in the northwest United States for more than 10 years and, in 2014, began consulting and managing builds in other states. Ken is an accredited ARCSA Professional Designer / Installer and Life Member, the Northwest Regional ARCSA representative and advisor to its education committee and is available to speak about Rainwater Collection Systems design and builds.

Ken is a United States Navy veteran, having served on active duty during the Vietnam War era.

A career entrepreneur, Ken created a new business focus with a commercial dive company in Hawaii in the mid 1980′s to respond to and clean up oil spills, oil spill equipment training, service and maintenance for the oil co-op service industry. Ken is passionate about having a positive impact on the environment and is also a founding director of BANK-ON-RAIN (2011-2014), whose mission is to create grassroots solutions for rainwater collection for consumption and agriculture in developing areas of the planet.