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Collect Rainwater During Any Situation

Monday, 19 November 2012 19:47 Written by 

A disaster has struck. Your reliable public water supply is no longer working; there is a power outage. You have procrastinated, or thought “a long period without power would never happen to me”, and have not stored any water.  Or, you did not know that most public and private water supplies require power to make your home’s faucets work. There is a small pond in your area, but the flood waters have brought debris, and sewage is running through the streets. To add to your troubles, your neighborhood is in total chaos from the disaster, and looters are going from house to house.  Does this sound familiar? Is this the start of another survival novel? No, it is what is going on right now in the Northeast following Hurricane Sandy.

Emergency officials were caught off guard, or did not plan accordingly, as they cannot provide the much needed supplies to the masses. You are thirsty. As the dreaded rain returns, you remember that you can collect rainwater. You rush helplessly to find containers to put out in your yard. You hear the sound of the rain gushing through your roof’s gutters and down the drainpipe, and into the street. A flood of water washes down the road. If only you had planned for collecting rainwater before the storm devastated life as you knew it.

Hindsight is 20/20. At least that is what we continue to tell ourselves. While, you cannot always prepare for every disaster, small steps can be taken to ensure your survival. Water is an abundant resource across the country, and if you live in a normally rain-blessed area, you will usually have a source of water. In order to collect a sufficient amount of rainwater, you should scale your collection methods appropriately. This is especially important in dry areas. Regardless of your environment, the general rule to collecting rainwater is: The more surface area you have, the more water you can collect. With the next rule being: The more storage capacity you have, the more collected rainwater you can store and use.

Rainwater Perspective

You can use the following formula to calculate how much rainwater you can collect per inch of rainfall:

Square feet of surface area x 0.6 = Gallons of water collected per inch of rainfall (SQFT x 0.6 = Gallons per inch rainfall).

A 1000 square feet roof can collect 600 gallons of water, per one inch of rainfall. Yes, 600 gallons! Knowing the average yearly total rainfall for your region, to include the monthly average, will allow you to project how much water you can collect, and when you will be able to collect it. Keep in mind, yearly weather trends can vary, and your totals should only be considered estimates; think of droughts. For the next example we will calculate how much water you could collect if you lived in the Virginia. The state of Virginia averages 44.3 inches of rainfall per year. Using the formula above, if you lived in Virginia you could collect approximately 26,580 gallons of water per year (using a 1000 square feet surface). Of course this depends on where you live in the state of Virginia, and how much water you can store. See where your state ranks (Using the list, select your state to see regional rainfall).

Let’s also look at this from a micro level. A 1000 square feet surface area may not be practical in a grid-down situation. If you have “Bugged Out”, you may only have a tarp in your Survival Bag. A 10x10 tarp has 100 square feet of surface area. Using the same calculation, the tarp could collect 60 gallons of water, per inch of rain. This is dependent on how you setup your tarp for collection; realistically you should be able to collect 35 – 50 gallons, per inch of rain.

Small Scale Rainwater Collection Methods

Place buckets, containers, and swimming pools (inflatable/rigid “kiddie” pool) to collect rainwater. Keep in mind, that by using these methods; makes your water source vulnerable to debris, insects, and animals. Transfer water to a “ seal-able or close-able” storage container if possible, or cover immediately following the storm.

Use tarps, or plastic/vinyl materials, to increase your surface area. You can purchase a tarp designed to divert water leaks in buildings, which contains a drain that can be connected to a water hose. Alternatively, you can purchase a large roll of plastic from your local building supply store, or use an emergency poncho (if you do not need it to keep dry).  Any budget tarp can be used, but we prefer polyethylene tarps for rainwater collection (lightweight and durable).

Use plastic sheeting (plastic roll) or pond liners to line a pit, or in the back of your truck bed. The flexible plastic sheeting can conform to any size hole, as long as it is large enough. Plastic sheeting also provides a barrier from contaminates in your yard or truck bed. If you are using a truck bed, keep in mind that your vehicle can only support a certain amount of weight. Most full size truck beds can store over 300 gallons, or approximately 2,500lbs of water. The average 150 / 1500 series truck cannot support that amount weight in the bed (average payload is between 1500 – 2000lbs).

If you plan on using plastic sheeting, we recommend a minimum of 4 mil thickness and 10 feet wide. The thickness provides more resistance to tears, and the width provides larger applications. If you need smaller sections, you could always cut it down. 10ft x 25ft, 20ft x 25ft. Plastic sheeting is a great all around purchase, as it can be used for multiple tasks; just get some. 

Large Scale Rainwater Catchment Systems

If currently live in an area that allows you to harvest rainwater, has sufficient rainfall, and you can afford a rainwater collection system, you can design a system that is integrated with structure/s on your property. There are many YouTube videos offering how-to’s. Here are a few we recommend watching.

Rain Water Harvesting Part I | Rainwater Harvesting Part II – Good system overview. The author also shows how to connect two harvesting systems.

Rain Barrel – Tip 1 – If you can get passed the music, provides a good overview of how to connect your rain barrels.

If you have a Kindle, and are interested in constructing your own system, we recommend reading Build an Extreme Green Rain Barrel. This book covers all aspects of rainwater harvesting, and is a great resource for planning, building, and managing your rainwater solution. If you want to purchase a kit, or prefabricated barrel, there are many options to choose from. Or, you can find food grade barrels or tanks locally.

IBC Tote - This video demonstrates a rain collection system using IBC Totes. 


Use Craigslist to find 55 gallon food grade barrels, or 275 gallon water tanks (also called IBC Totes). Please ensure you know what was previously stored in barrels or tanks you intend to purchase. Some of these may have been used to store fuels or chemicals.

When selecting barrels, color plays a big role; not for cosmetics, rather for algae growth. Algae naturally occur in most water sources, when the water source is exposed to sunlight. If your rain barrels will be used to water your garden, algae may not be a bad thing since it provides nutrients to your plants. But, if your rain barrel will be used for drinking/cooking, then you will want to stop algae from growing. There are multiple ways to restrict algae grow, and the color of your rain barrel is the first defense. Dark colored rain barrels are preferred (think the black food grade barrel), as they restrict light penetration. Blue barrels are the next choice.

There are several methods you can use to combat algae growth: 1) paint the outside of your rain barrels black. 2) Add two ounces of bleach to your rain barrels when they are nearly empty. 3) Cover your rain barrels with a tarp, or bury the rain barrel. 4) Place your rain barrel on the shady side of your house. 5) Use the water in your barrel before algae grows.  

Alternatively, you can install a cistern on your property. A cistern can be above or below ground, and follows the same general concepts of barrel; just on a larger level. Cisterns can be made out of food grade plastics, metals, and/or concrete. You will need to balance the cost of multiple rain barrels, or one large cistern. Cisterns store more water, and in the long run may be cheaper, but can become a single point of failure.

If you live in a community that has a rainwater collection pond, you may be able to use that as a water source. Keep in mind that any water taken from a body of water will also contain the chemicals that are used in our yards. This is extremely important to understand in heavily developed areas. We [Americans] like green yards, and with green yards comes chemical treatments and fertilizers. These chemicals can make you sick, can cause cancer, or can kill you if consumed in high doses.


In most areas of the country rainwater can be harvested for consumption and agricultural uses, even when the power is out. It is important to gather the resources now, before a disaster was to strike. And, even if you do not have the resources stockpiled, there are still ways to collect rainwater; you just might do it on a smaller scale. When using rainwater, or any non-potable water source, keep in mind that you will still have to purify the water (through boiling, filtration, and/or chemical treatments) before it can be consumed. Read our Water Filtration Article

Last modified on Tuesday, 12 March 2013 18:09
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