Category Archives: Rainwater Catchment

How-to, Rainwater Catchment

Rainwater Collection in Washington State: Where to Begin?

gutter-484684_640We want to keep our families safe, but when we read stories about sustainability, water conservation, saving the environment, aging infrastructure, even poisoned public water systems – how on earth are we supposed to know where to begin when it comes to rainwater collection?

Here are some tips that can help you decide where to begin. We originally discussed this in a post from 2014:

Whether you are designing your own rainwater catchment system or having one designed by a professional, success of your rainwater catchment system design is dependent on some key factors.

What do I want to accomplish with my design of a rainwater catchment system?

Irrigation, toilet and or laundry facility, supplementary to well water or city water, whole house usage, and sole source are the main purpose of designs.

How much rainwater can I collect from my roof? Will it be enough to supply my needs?

One inch of rainfall per 1,000 square feet of roof will yield approximately 623 gallons of water. Evaporation, wind, and spillage account for 15 – 20 % of loss. A 2,000 square foot roof with 36″ of annual rainfall may yield 44,856 gallons. With an efficiency of 85%, that equals 38,128 gallons.

One inch of rain is needed for the healthy growth of plants. This equates to .623 gallons per week for 1 square foot of planting, which can add up rather fast, so keeping your irrigation needs small and giving consideration to drought tolerant plants is recommended.

Toilet and laundry facilities account for 49% of household usage. Designing and building a system for this purpose alone can cut your water and sewer bill in half. New construction is the best time to implement this type of system however, retrofitting plumbing in an existing home can be accomplished.

Rainwater Catchment System Key FactorsIf the collection area is small or available space for storage is restricted, a supplementary system can be achieved with “slim line” style of cisterns or buried tanks. A small roof can still be effective in collection if used for a supplementary source to well water or city water.

Whole house usage, or potable water, can eliminate dependency on city water or well water, where you can still have city or well water as a back up during dry times. With the advanced filtration and UV disinfection offered today, safe, reliable drinking water for whole house usage will exceed the quality of most well and city water.

Now that you are considering what usage of collected rainfall would best suit your needs, we will discuss sizing, configuration, implementation, and maintenance of a designed rainwater catchment system in upcoming posts.

When you are ready to begin, RainBank will come to your site, discuss your needs and prepare a feasibility study – customized to your usage. There is a fee for this, which would be discounted from the cost when you contract with us to design or build your system. Use the form below to request a quote.

Rainwater Catchment, Water Tanks

Considerations for Underground Water Storage Tanks

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Xerxes underground tanksRainBank is experiencing increased interest in underground storage for our Seattle customers, requiring special considerations for underground water storage tanks.

Aesthetics and available space are the most common reasons from these customers. Many are building larger homes on small lots that once had a 1,200 square foot home with a front and back yard. New construction is trending towards a larger footprint, leaving less room for water storage tanks. Slimline tanks allow for less visual impact, but are restrictive on volume. Other residents are remodeling older existing homes that still have yard space available – and are looking for greater amounts of storage.  Below grade storage can be the answer, leaving a yard area that can accept landscaping right over the top of the water tanks.

Here are some things to consider with underground storage.

  • First and foremost – costs. Below grade storage will require excavation and. most likely, exporting much of that soil, which would have to be loaded and trucked off site.
  • Drainage needs to taken in account, with the new City of Seattle stormwater rules preferring infiltration for overflow. Where infiltration is not feasible, connection to the city storm system can be implemented for overflow as long as caution is taken to prevent sewer gases  or back flow from entering the tank.
  • Water tanks need to be properly vented and have a riser to access the tank for periodic cleaning and pump service. The installer must be sure that plumbing will not be compromised with slight settling or shifting of the tank.
  • Below grade tanks tend to be more expensive to meet engineering requirements of underground tanks, and once installed, are considered a confined space and caution must be taken if access is necessary. 

Underground-Tank-Construction3-1038x576For those who understand the considerations of underground storage, you have the luxury of landscaping that is free of visual impact and have different available options in tank sizes, styles, and materials. Tanks can be single or multiple, plastic or fiberglass. Cement tanks can be used for non potable use or lined with a NSF certificate for drinking water. 

Potable, Rainwater Catchment

Proactive in the Advancement of Rainwater Collection

mt.rainierRainBank has always been proactive in the advancement of rainwater collection. We designed and built the first potable system in Seattle, as well as the first potable systems in Skagit, Jefferson, and Whatcom Counties.  

Additionally, we have been designing and building rainwater collection systems for potable and non potable demands for more than 15 years throughout Washington and Oregon.

RainBank began in San Juan County, which at that time, was the only county that allowed rainwater harvesting in the state. San Juan County had an exemption to the state’s water rights laws that considered rainwater a tributary and therefore not subject to those laws. It wasn’t until 2009 that Department of Ecology convinced the legislature that rainwater collection was beneficial and therefore should be allowed. More counties began to come on board to allow  the use of treated rainwater for potable use, with King County adopting in 2011. Since then, many counties in Western Washington now allow the practice, but there are still those who have not.

We were recently contacted by a customer from Wahkiakum county in southwest Washington, who wished to use rainwater collection for potable use on his property. The spring that was grandfathered in did not pass the last well report and was deemed unsafe for consumption. I petitioned the county health department for acceptance of a sole source potable system and was told they never heard of the practice. I sent documentation from Department of Ecology, King County policies, ARCSA (American Rainwater Catchment Systems Association), a list of Washington counties that have adopted rainwater use, a few case studies, and our website.

I am pleased to announce that Wahkiakum County responded that they will consider a design for residential potable use for this project.

It is through experience, expertise and commitment that RainBank Rainwater Systems is the leader in Washington State’s rainwater catchment industry.