Posted by: rainworks | November 22, 2014

RainBean System Design

Capture it, Don’t let it get away? 

Quality Harvested Rainwater requires a Harvesting Infrastructure that will insure the cleanest water at the Point of Entry (POE) of the water storage Cistern which can be stored over a ‘period of time’ for various uses; be it a non-potable, or a potable resource.

Harvested rainwater should be very clean and not contain; Debris (organic or inorganic), Metallic taste, Hard water tastes and smells, Pharmaceuticals, Pesticides, Herbicides, etc.

Rainwater has a pH generally around 5.6, it is still potable, but it will be slightly acidic (mildly corrosive). Aerating it (from bottom to top) will help increase the pH by increasing the CO2 (Carbon Dioxide), and O2 (Oxygen) introduced by aeration. A Neutral pH of about 7 is desirable. There are alternative additives that can be used to control pH levels, and a First Flush device works as well.

The Rainwater Harvesting Infrastructure – Top Down

Preliminary Infrastructure

The Roof: (should use licensed contractors)

Safety and Quality are paramount concerns. This includes equipment and professional knowhow, will generally have required community codes, permits, and inspections. Ensure your contractor is knowledgeable about the use of suitable materials for rainwater harvesting. (See references at bottom of this document.)

The Gutter and Downspouts: (should use licensed contractors)

Proper gutter sizing, knowledge of slope of roofs, normal rain intensity, distances between downspouts/roof perimeter, etc. Ensure your contractor is knowledgeable about the use of suitable materials for rainwater harvesting. The use of “Leaf Guards” is highly recommended. (See references at bottom of this document.)

RainBean System

Secondary Infrastructure

The Diverters:

The First Stage Diverter’s purpose is to remove large debris, such as; leaves, pine needles, twigs, seeds, roof particles, and other contaminants from getting to the pre-filter. The rejected debris is ejected into the downspout, while filling the Second Stage Diverter. This is accomplished through an 18 mesh (0.038in/0.97mm) stainless screen into the chamber containing the Pre-Filter.

The Second Stage Diverter serves two functions; self-cleaning of the Pre-Filter of much finer accumulated debris such as; smaller hayseeds, seed hulls, pollens, smaller roof particles, and directing that finer debris into the downspout, as the rain event recedes. (This eliminates much of the maintenance-required with other filter systems.) However, it is recommended that annual or semi-annual inspection or maintenance be undertaken, otherwise it may only require inspection just prior to normal rainy seasons.

The Pre-Filter

RainBean’s Pre-Filter system uses passive intake for ambient rainfall pressure to extract the rainwater from the Second Stage Diverter chamber, (which is potentially laden with even smaller debris that passed through the First Stage diverter). The Pre-Filter cartridges come in: 80-200 mesh (0.08in/0.18mm) – (0.0029in/0.07mm) in size and are user interchangeable.

At this point one may have about 95-98% rainwater Harvesting efficiency due to the minor diverter wash-off losses.

But then, that is not enough!

For the cleanest rainwater, a First Flush device was added to the RainBean System.

First Flush:

To further improve the quality of the rainwater going into the Cistern, a First Flush device became an integral part of the Harvesting Infrastructure.

This is typically a small tank, of which the initial Pre-Filtered rainwater is first collected during the initial roof wash off cycle (graywater). The tank is sized by a calculation of; roof footprint, roof material type coefficients, and pollution factors. Once that required calculated amount of rainwater fills the First Flush tank, a valve actuates and re-directs remaining Pre-Filtered, improved quality rainwater into the Cistern.

The purpose of RainBean’s First Flush is to collect and withhold any remaining initial cloudy roof wash off rainwater that can contain micro particulate, such as; dust, pollens, bacteria, decomposed insects, soluble bird and vermin droppings, roof/gutter material (Grit and heavy metals), and chemical pesticide and herbicide residue resulting in what can be called greywater.

During and after a rain event, the tank will slowly empty the resulting graywater via a 1-4 GPH drip fitting either directed to a storm drain or landscaping.

Rainwater storage:

A most serious concern when harvesting rainwater is to collect as much as possible when rain events occur.

  • The Cistern or tank farm sizing requires calculation of data: number of users, interior and exterior household water requirements. (Business and commercial clients should require similar calculations.)
  • Research is first required of existing Climate resources to prepare calculations for all rain events monthly and annually per the installation’s location. Monthly sizing should take into consideration the historic driest months of the year, and design the total storage capacity to use cumulative stored rainfall to withstand the needs for those drier months.
  • The RainBean System uses a Damping Aeration input pipe, maintaining oxygenation of the stored rainwater volume at various levels during intermittent rain events. The oxygenation helps destroy any possible harmful bacteria also known as anaerobic activity of which such bacteria cannot survive in a rich oxygen rich environment, and helps raise the pH.
  • The RainBean System also includes a tank overflow downspout, to be the same size as the POE input size. It also uses a simple PVC Backwater Valve to prevent insects and other vermin from entering the cistern from the overflow downspout.

RainBean System Materials:

  • SDR-26 PVC pipe, Schedule 40 PVC pipe and fittings with NSF–pw (Potable Water rating), and Stainless steel screens.
  • The RainBean Slim 3 has a 4” diameter input coupling, which accepts various size gutter input connections, using COTS adapters for 3” diameter, 2” x 3” and 3” X 4” roof downspouts.
  • The bottom has a 3” downspout connection and a 3” connection to the POE of the Cistern.
  • The RainBean is paintable to match any color scheme.
RainBean Slim 3 with Adpt

RainBean Slim 3 with Adpt


The RainBean can be mounted on a standalone pipe or downspout, or mounted to the exterior wall near the gutter output. The RainBean is first connected to the gutter, secondly it is connected to the First Flush Unit, and then to the Cistern. For overflow, it can be connected to the RainBean downspout, or connect to a separate downspout,

A complete installation manual will be included with each RainBean System.

Photo Report During One Rain Event

RainBean instal with labels

RainBean System Configuration

  1. RainBean Dual Stage Diverter/Pre-Filter
  2. Pre-Filter Output
  3. First Flush Tank
  4. End of First Flush – Valve
  5. Clean Water Input Damping Aerator
  6. RainBean Debris discharge downspout
  7. Overflow – with insect, vermin entry protection

RainBean top view

Top view of a RainBean System Configuration

One Rain Event: two roofs, showing capture efficiency.

RainBean Debris discharge downspout showing only dual diverter discharge and First Flush Dripper

RainBean Debris discharge downspout

Rear roof (640 sq. ft), “Rainwater captured”. Diverter discharge and First Flush dripper discharge. (Balance of rain entered Cistern.)


Front roof (537 sq. ft), “NO capture”. All rain directed to a storm drain at same time during the one rain event.

First Month of Harvest Data

(To be announced)

Using Rainwater from the Cistern, Point of Use (POU)

Plumber for POU: (should use licensed contractors)

At the POU Cistern output, it is recommended to include a .5 micron Carbon Block filter which will remove cysts such as Giardia and Cryptosporidium, most chemicals, and carbon black particulate (from fossil fuel exhaust). Add a UV filter, for the ultimate sanitization. If attaching to an internal home potable fresh water system while using a public water service, the addition of a back-flow preventer is highly recommended, and is required by law in many locations.


Consumed with my past practical experiences (including failures), learning new and innovative techniques, and with continued research to understand how important rainwater Harvesting is a life saving resource on a highly populated planet. I have designed and built several prototypes to create a quality Rainwater Harvesting System. There always seemed to be just one more component to add or modify. On a limited budget, this latest system design has completed my goal of creating the best of rainwater Harvesting Infrastructures, lead me to finally file for a patent and start testing my final system designs.

A quality built Rain Water Harvesting infrastructure will provide clean water to the storage Cistern(s). Proper sizing of the Cistern(s) should provide clean Rain Water throughout the year. My goal is to achieve a global Rain Water Harvesting System to help stabilize the availability of clean fresh water resources for the inhabitants of this planet. The System will be composed of supplying various kit components, fittings, and instructions to contractors, off the grid customers, and DIY enthusiasts.

Three models of the RainBean will be available.

The RainBean Slim 3, a vertical model, suitable for a roof footprint up to 750 sq. ft.

The RainBean Plus 3, a horizontal model, suitable for a roof footprint up to 1200 sq. ft.

The RainBean Ultra 4, a horizontal model, suitable for a roof footprint up to 2000 sq. ft.

As well, various other required system components will be packaged in several boxes, whether a new complete system, or retrofit an existing preliminary infrastructure. The user need only complete the preliminary infrastructure, size and purchase appropriate storage Cisterns, needed lengths of pipe, install a secure base for above ground Cisterns or in ground Cisterns.

Software Application:

A software application is in development for the PC and Smartphone. This App will help provide the user with the ability to calculate;

  • Roof footprint
  • Roof material type coefficients
  • Pollution factors
  • Size the Cistern(s) for; domestic, agricultural, and commercial facilities
  • Provide component(s) installation metrics; gutter to ground, First Flush, etc
  • Water demands; Indoor and outdoor water use as per user requirements
  • Garden and Landscaping water use for Drip Irrigation components
  • Utilize global climate/weather resources for users location

I welcome comments and questions on this post, and I will maintain future updates.


(Prefiltration standards Linkedin ARCSA)

Denis Rochat

President at rainwater Resources

IGCC 2012 calls for 1500 microns of pre-filtration, ARCSA/ASPE calls for 500 (.5 mm). We utilize Vortex filtration that filters to 280 microns and provides extreme oxygenation. Both are critical for healthy stored water. Successful systems require several steps that make up a process and none can be ignored. I saw a 10,000 gal RWH storage in Roanoke, VA that had not been cleaned for 7 years and provides slime free, odor free, color free water every day. That’s the goal.

American Rainwater Catchment Systems Association ARCSA – Resources and Documents

Texas Water Development Board The Texas Manual on Rainwater Harvesting



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