Did you know that if you have 1,000 square feet of roof and it rains an inch or two one day, that one rainfall has provided you with 600-1,200 gallons of water falling from your roof?
Here’s how to make use of all that water!
WHAT YOU’LL GET BELOW
– Videos on how to build a rainwater catchment system
– Important things to avoid when building your system
– Methods of storing, testing, and purifying that water
Here we go!
In a SHTF scenario, having a rainwater catchment system will benefit you and your family in several obvious, and not-so-obvious ways.
Obvious and Not-So-Obvious Benefits
We need water to drink, cook, bathe, clean, and grow crops, edible plants , and livestock. Obvious ways.
But if the grid goes down and stays down, how valuable will that rainwater catchment system, and all the potable water it provides, be?
The not-so-obvious benefits — your rainwater catchment system now becomes a power plant of value for you and your family, offering commodities and skills that others will NEED!
This brings with it a host of other considerations, like concealment, protection , and how to best trade your new found resource.
But these aren’t the focus of this article.
The goal of this article is to bring together all the resources you’ll need to get your system built and running safely.
Materials To Use – What’s Safe?
Many of the materials we use in building our houses leech toxic chemicals into rainwater.
It’s important to know what you’re building your catchment system with, and the potential risks, before you start spending your money and time.
Looking to places where these systems are relied on today will help give us useful tips for building our rainwater catchment system tomorrow.
Did you know that 30,000 to 60,000 people in Hawaii depend on rainwater for survival?
With that many people using rainwater all year round, Hawaii is a great place to start.
From The University of Hawaii’s College of Tropical Agriculture and Human Resources Cooperative Extension Service Hawaii’s Pollution Prevention Information 
The condition of your rainwater catchment roof, gutters, pipes, and tank affect the potential for contamination of your water supply. This is especially important to consider if you use your catchment water for drinking.
You should be concerned about the system’s surroundings, condition, and maintenance. Some contaminants in water may affect only appearance, while others such as bacteria, nitrate, and toxins can be extremely harmful and even fatal.
Are the roof, pipes, or faucets made or coated with toxic materials?
Many roof coatings, paints, and collection materials contain toxic substances that can contaminate your tank water. For example, galvanized roofing is a source of zinc, roofs with copper flashing can have high copper and lead concentrations, and some roof coatings and roofing nails contain lead.
Old copper pipes may contain lead solder, and brass faucets may also be a source of lead. You should consider replacing these materials and components or treating them with coatings that are made of nontoxic materials.
Texas A&M Rain Harvesting Center  offers a collection of articles covering safe materials, safety guidelines, and a whole slew of other useful resources, including:
NSF International has developed a test protocol that provides independent verification of the safety of the materials used in the production of rainwater harvesting systems. This protocol evaluates materials used in rainwater catchment systems, such as roofing materials, coatings, paints, liners and gutters.
Testing involves exposing catchment system product samples to extensive accelerated outdoor weathering. The systems and system materials that have successfully been tested by NSF under P151 are listed in the NSF Product and Service Listing
Rainwater Catchment System Tank Size?
Here, bigger isn’t always better.
You’ll want to size your tank according to your needs as well as what the environment can provide.
This is all about efficiency and cost.
First, check out the National Climatic Data Center and figure out roughly how much rainfall your area will get in the following year.
You’ll want to know this for month-to-month, preferably going back approximately 10 years, so that you can accurately use the University of Warwick’s Rainwater Tank Performance Calculator .
From their site:
As the cost of a domestic rainwater harvesting (DRWH) system depends mainly on the size of the tank, it is important to design the tank to ensure optimum performance at tolerable cost.
This programme calculates the approximate system reliability and efficiency for a selection of tank sizes including one that you can define, using your monthly rainfall data and roof area.
You can also define how the rainwater will be used by giving a nominal daily demand and choosing between three water management strategies. By looking at the reported performance for all the tank sizes, you can change your chosen size, nominal demand and management strategy until it reaches an acceptable performance level.
The University of Hawaii has a very detailed Rainwater Catchment Systems PDF  which includes:
1 Water collection—how to catch the water, how much water you need
2 Water storage—what to keep it in
3 Catchment system maintenance—identifying problems, keeping the tank clean
4 Water treatment—sources of water contamination, principles of water treatment
5 Water testing—keeping tabs on water quality
6 Firefighting concerns
Remember, 60,000 Americans living in Hawaii can’t be all wrong.
This PDF is in-depth, and there are links to additional resources at the bottom of this post.
Here are several videos from Texas A & M showing basic construction, as well as different applications of a rainwater catchment system.
This first video is an introduction into the benefits and uses of a rainwater catchment system.
Here’s an example of using this system at a hunting cabin.
They call this a “rain barn” and you’ll see why
This video shows how they use rainwater capture systems on the Freeman Ranch. Pretty neat!
For use on a greenhouse
These next two videos are particularly cool. They’re rainfall simulators.
And if you want some hard-core manuals used by relief workers in the field, please check out the WELL Intranet .
From their site:
Originally published individually in Waterlines, the world’s only magazine devoted entirely to low-cost water and sanitation, these highly illustrated technical briefs bring together a body of information and guidance which has already proved of great practical help to agencies and fieldworkers.
Hope you’ve found this resource useful.
What’s your biggest challenge with making your own rainwater catchment system? Tell me in the comments below, and I’ll do my best to find a solution!