Tag Archives: supplement city water

Rainwater Catchment, Residential Rainwater Collection

Swimming Pool Repurposed for Underground Rainwater Collection

underground tanks former swimming pool7,200 gallons of collected rainwater for household usage has no visual impact for this newly constructed Bellevue home. The homeowner wanted to have a rainwater catchment system to provide water for the toilet and laundry facility, but he did not want large, above ground water tanks interfering with the landscaping of his backyard.

Residential Underground Rainwater Collection Tank-AfterThe solution: excavating the old cement swimming pool and placing four 1800 gallon poly water tanks in its place, creating an underground rainwater collection system.  All the tanks are connected with a manifold for equalization and supply a pressure tank and filtration in the mechanical room for usage. Solenoid valves provide automatic switching from rainwater to city water if the tanks should run low, but will switch back to rainwater when the tanks receive more water from the roof.

Gutter screens were installed, along with a vortex filter, which will eliminate debris from entering the storage tanks. In the mechanical room, a sediment filter will remove fine sediment, followed by a carbon filter to eliminate color and odor.

With auto switching, the homeowner will never know the difference (other than his reduced water bill) and he finds the underground rainwater collection system aesthetically appealing.

How-to, Rainwater Catchment, Residential Rainwater Collection

Rainwater Catchment System Key Factors

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Rainwater Catchment System Key FactorsWhether 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.

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