Rainwater systems

Article written here based on below links forthcoming.

Introduction

A rainwater harvesting system showing overflow functionality.

Municipal water networks are vulnerable to disaster events like earthquakes, flooding, pollutants and water shortages caused by drought or poor management. With a rainwater system a home or community can capture and collect water suitable for drinking, cooking and gardening even during periods where there is insufficient rainfall to satisfy the public water network. Other benefits cited by the collection of rainwater include reducing expense (in regions where water supply is not free), lowers local demand on freshwater resources, reduces risk of flooding in low-lying areas and slows erosion in dry environments^[1]. Water is typically captured from a sloped roof, but it can also be captured from a structure deliberately built for the purpose.

Rainwater collection calculator

Formula

The formula to calculate the rainwater collected (RC):

   RC = A * R * C

Where:

   RC: Rainwater Collected (in liters or any desired unit)
   A: Collection Area (in square meters)
   R: Rainfall Intensity (in millimeters per hour)
   C: Collection Efficiency (expressed as a decimal or percentage)

Here, A could represent a roof area, and C is the effectiveness of your rainwater collection system. It takes into account factors like runoff, leaks and losses. You can express it as a decimal (e.g., 0.75 for 75%) or a percentage (e.g., 75%)^[2].

Example in metric

Suppose you have a collection area of 60 m², a rainfall intensity of 10 mm/h, and a collection efficiency of 65% (0.65 as a decimal).

Using the formula: RC = 60 * 10 * 0.65 = 390 liters

390 liters of rainwater can be collected in this scenario.

Rainwater collection methods

Rain Barrels

Picture of a 'rain barrel' with down spout from roof collected rainwater.

This method is the fast to get setup with and popular as a readily available backup solution. It involves installing a barrel at a gutter downspout to collect rainwater. The actual barrel may be a recycled barrel or a commercially available rain barrel. Some commercially available barrels are made of food grade plastics. UV resistant plastics can be a good idea, especially if the barrel cannot be installed in a location away from direct sunlight.

Pros:

Easily implemented by anyone at any residence
Barrels are readily available in your community or at various stores & websites
Barrels don’t take up much space so they can fit into any situation

Cons:

Capacity is generally small with the commercially available barrels
It can easily overflow and so wastes water collection opportunities

Linkdump

Great overview of home-scale rainwater systems, with some handy calculations (Imperial) to help think through needs and supply

https://www.treehugger.com/beginners-guide-to-rainwater-harvesting-5089884

And another 101/overview, with a functioning roof surface catchment calculator

https://www.watercache.com/education/rainwater-harvesting-101

Article on care and cleaning of rainwater tanks

https://rainwaterharvesting.org.au/care-maintenance-of-rainwater-tanks/

Great collection of helpful images on rainwater harvesting

https://www.pinterest.ch/ServiceHomeTholen/rainwater-systems-regenwater-systemen/

Interesting article of a very low cost solution using multiple steel barrels

https://survivalblog.com/2017/04/19/rainwater-harvesting-an-easy-and-efficient-build-by-l-r/

The same low cost 'rain barrel' system outlined here, fed by downspout. This looks ideal for water infrastructure disruption fallback, to tie a household over for a week or so. They cite USD150 total cost:

https://www.treehugger.com/make-rain-barrel-system-at-home-5194982

Citations

[1] ttps://www.treehugger.com/beginners-guide-to-rainwater-harvesting-5089884

[2] ttps://savvycalculator.com/rain-collection-calculator/

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