Tag Archives: design

Key Factors In Planning a Rainwater System

Water. We simply can’t live without it. Safety, cost and convenience are some key factors to consider when planning a rainwater system for commercial or residential use. Will the water be used for irrigation? Toilet or laundry facilities? Or, will you and your family want to drink it?

Here are some key factors to help you decide where to begin designing your system. 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.

If 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 feasibility study.

Rainwater Systems Designs

ruler-1030968_640RainBank Rainwater Systems designs potable and non potable rainwater catchment systems throughout Washington, Oregon, and Idaho.

RainBank’s experienced team provides customers with an integrated, progressive approach to sustainable, premium water systems.

Our customers include;

  • Eco-friendly homeowners seeking to add rainwater collection or integrate into plans for a new premium or custom built residence
  • Architects developing plans for premium residential projects
  • High-end building contractors specializing in custom builds
  • Commercial contractors where rainwater harvesting is a component to the scope of the project

We work closely with our clients early on in the project to insure the system design will meet the client’s needs and desires. We spec only quality components, chosen based on our 15 years of experience, ensuring performance for years to come.

RainBank is a full service LLC with in-house engineering, design team, and licensed plumber. Our designs meet all county and state plumbing codes and their requirements. RainBank is familiar with the permitting process in most counties and will process the permitting to alleviate the guesswork for our clients. Our designs include;

  • Calculations of domestic demands & supply, MIDs, & sizing 
  • Drawings from down spout to storage, cistern placement, conveyance, filtration train, connection to household  and civil
  • Complete list and specs of components along with manufacturer cut sheets
  • Operations and maintenance manual
  • County permitting from health department

We install our own designs to ensure the system will meet the high standards we have set in the industry. We offer inspections of other systems for evaluation, real estate and insurance transactions, always with a detailed written report including sampling results and photos for submittal.

RainBank’s team is ARCSA  Accredited & ARCSA  Inspector Specialists.

Need more info? Contact us below:

Consider Future Demands on Rainwater Collection System

rain-gauge-907678_640When you calculate area rainfall – measured annually, monthly and daily, plus factor in how the water will be used in the future, you can determine how much is storage is necessary to meet your needs.

Being aware of current water use is helpful with knowing how to size a system, but don’t neglect to consider potential future demands. If you’re planning a family, entertaining, have a growing business, or may sell the dwelling and property, you want to account for those scenarios when you calculate storage. At best, the system should be professionally designed and built to meet future demands as well. Here are more reasons to consider future demands when building a rainwater collection system:

Possible drought or longer periods of dry season should also be considered when designing or building a system. Incorporating back up water supplies into a system can be as easy as hauled water, or drawing from a well, community or city water system and should be an available option for those times. Residential rainwater systems in the city are often limited in space for storage, leaving the volume of the cisterns inadequate for year round use. Having the ability to switch to this alternate source can be a necessity in design. However, a more rural environment lends itself to larger storage capacities.

Water demand is an important part of design and the American Water Works Association (AWWA) has conducted a study of various fixtures and appliances. Knowing these demands will help estimate usage and assist the designer to adapt the design accordingly. Single flush toilets use 1.28 gal/ flush, dual flush toilets 1.0 gal/ flush for liquids and 1.28 gal/ flush for solid. Average use is 6 flushes per person, per day. Low use fixtures such as shower heads, faucets, cloths washer (front loading) are recommended for the overall design of the house and can be found in publications from manufacturers.

Outdoor demand should be limited as much as possible. Drought tolerant plantings, drip irrigation, and general conservation will help limit outdoor usage.

For specific irrigation needs, Evapotranspiration (ET) is the measurement of amount of water in inches that is needed to grow plants. All plants have a different watering requirements, also being affected by temperature, wind, humidity, and sunlight. A state climatologist can be contacted to attain an ET standard reference for your area. Careful consideration of outdoor use must be given if irrigation is part of the RWC design. An average city lot can use as much as 1,800 gallons of water for watering a lawn.

In order to get the best performance from your rainwater collection system, indoor and outdoor demands must be carefully calculated using best storage capacities, surplus and defect, level of storage, daily, monthly, and annual use/demand for the entire year. Simply calculating the average annual rainfall amounts will not produce the end goal of a well designed RWC system. It is best to determine average potential of collection and use. Determine average daily, monthly, and annual rainfall amounts. Calculate collection area, and determine runoff. Identify highs and lows of rainfall amounts and demands. Determine those months of low amounts of rainfall along with the carryovers from months prior. Certainly, identify those months of zero rainfall.

When you know how you currently and potentially will consume collected rainwater, plus install water efficient fixtures and by employing best conservation practices, you will have enough during periods of high demand or drought, when you might have to cut back or switch to an alternate source. If you plan for this during the design process, you will have a system that works for you far into the future.

This article was originally published under the title Estimating Water Usage for a Rainwater Collection System at RainBank.info