Tag Archives: rain garden

Rainwater Catchment

Change Your Way of Thinking About Rainwater Collection


A young orangutan holding a leaf umbrella in the rain.Collecting the rain makes better sense than complaining about it. Whether you collect it in rain barrels or your storage needs require larger cisterns, rainwater collection and use has a host of benefits. Here is why you should change your way of thinking about rainwater collection:

Rainwater can be a clean, safe, reliable source of potable and non potable water. Rainwater is relatively clean to begin with and if collected, conveyed, stored, filtered and disinfected properly, it can meet the needs of small scale watering to whole house potable use.

Rain barrels can collect water inexpensively for small watering needs, with down spouts being diverted to a rain garden when full, as well as during the rainy season.

Larger cisterns can collect water all winter long to have a large volume for irrigation needs during the summer months. If collected water is pressurized and filtered, it can be plumbed into toilet facilities and laundry to supplement city water usage. If filtered and disinfected, whole house potable usage can be achieved whether large cisterns are used for year-round use or as small storage as asupplement to city water.

So, instead of saying “DARN RAIN!!!!”, consider changing your way of thinking aboutrainwater collection.

Orangutan in The Rain (c) Andrew Suryono, Indonesia, Entry, Nature and Wildlife Category, Open Competition, 2015 Sony World Photography Awards

Residential Rainwater Collection

Cement Cisterns Collect Urban Rainwater

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With limitedspace in urban areas, cement cisterns are being built beneath homesas a rainwater harvesting solution.

A narrow, covered passage with a person lying inside.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 solvethis issue is with a cement vault, constructed beneaththe 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.

Person spraying concrete or plaster on a wall in a construction setting.Cement water tanks are not naturally waterproof; cracks in concrete can resultyears 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.

Rainwater Catchment

Potential Unexpected Costs From GSI Mandate


A round metal grain silo in a grassy area surrounded by trees.The GSI mandate or “Green Stormwater Infrastructure” can create unexpected costs for new commercial and residential construction.Controlling stormwater through GSI compliance requires on-site infiltration and/or use.

Roof runoff, along with impervious surfaces,contributes tooverwhelmed stormwater systems, which may result in pollutants entering our waterways and wetlands. A design using both methods of rainwater collection and infiltration can be the most cost-effective, while being beneficial to the environment.

A serene garden pond surrounded by rocks and lush greenery.Directing roof runoff for irrigation, toilets, laundry, or even pre-infiltration potable water, will reduce costs frommunicipal water supplies. During the rainy season, collected water can supply these uses while overflow from the cistern can be directed to infiltration.Irrigation in the summer months being supplied by the desired amount allocated from storage will enable the rain garden or infiltration system to be sized for a smaller amount of runoff while supplementing city water usage.