open-source rainwater catchment methods and kits

portland, oregon
We are all Makers. We believe in Open Hardware
. If something is truly for the greater good, it is not a secret. We are compelled to publish the methods of collecting, delivering and building rainwater-related catchments that we think folks should know about (including the ones we offer for sale)... Sometimes we hope you buy a kit from us, and other times we hope you'll try and Do It Yourself. In fact, we'll help you either way.


Contain Rain "Water-Arm" (intake + overflow) APPROVED
The Garden Watersaver™ (intake + overflow) APPROVED*


Bottom-Link / Top-Vent APPROVED


3/4" Spigot / Drain / Hose (+Drip Irrigation) APPROVED
Self-Hydration / Soil Wicking APPROVED
Electric Pumps (AC/DC) TESTING
[Please note: These illustrations are concept-proofs intended to describe the flow of water and air through a system; they do not reflect final system/kit design. For complete systems, see our kits page.]

Extraction Method

Soil Wicking

a. Water enters system through intake/overflow.

b. Water is collected and stored by a rainwater harvesting method.

c. A small cistern with a float valve regulates the water level in the hydrating beds. All beds must be on the same atmospheric level.

d. Soil sits atop gravel or sand; small starter pots filled with soil act as wicks—effectively hydrating the soil as its water evaporates or is used by plants.

e. Additional beds may be added to the siphon. All beds will be regulated by the water level in the small cistern (c.)

Micro-Climate Systems

How do your Self-Hydrating, Soil-Wicking Garden Beds work?

The system is inspiringly simple. You catch rain. You divert a few barrels to this system, say, one (55 gallons) per two beds (12 sq ft). The barrel is joined to a cistern with a float valve, which turns the water supply on and off according to the specific level of water it is adjusted to maintain (your toilet has one of these so it does not overflow when filling after a flush). The barrel-beds are leveled out and connected with tubes so that they will all contain the same amount of water as is present in the cistern. Each barrel-bed is filled with gravel and sand above this water level. The dirt in the bed sits atop the sand, staying relatively dry. And now here's the trick: Small 4" plastic planters are evenly distributed and dug into the sand. These planters fill with water. Dirt connected to the soil above is packed into them, transforming them into wicks (like in an oil lamp) employing the principal of capillary action. These wicks work against gravity to absorb water as needed into the soil. The soil will not become completely saturated, but will maintain a consistent moisture level. With good soil, this creates an ideal environment for plants to grow. By defining an impermeable bed space with the barrel, the system can conserve a great deal of water, and requires zero maintenance. Simply plant and harvest.

It is possible to conserve an even greater amount of water by minimizing the amount of evaporated water released from the top of the bed. This can be accomplished by placing another impermeable layer (such as plastic) around the base of the plants you are growing. In fact, we suspect that you might be able to get through the entire three-month Portland dry summer on one rainbarrel (55 gallons) per two grow beds. If you had 8 beds, that's nearly 50 sq ft of garden space on 4 barrels (only 220 gallons)!

For more detailed reading about this system, see the Self-Hydrating Garden Bed kit FAQ

What is the ideal method and schedule for optimal watering?

On the one hand, the answer to this question is simple and intuitive. We kind of know how life goes and how it works, and, for the most part, we can intuit the best way to water plants. Not too little, and not too much—right? On the other hand, when you begin to consider that water is one among a few different elements of concern, all interacting differently with one another depending on the particular environment... then we tend to get out our books and start scouring the internet for advice on raising our plants.

If you, first of all, remember to water, and furthermore, view your opportunities to water as sacred communal acts consummating you and the natural environment... then THAT is clearly the best and most effective method of watering we imagine a plant could ever hope for. For the rest of us who wish we enjoyed every moment of watering, the watering can is of marginal effectiveness. It is sometimes unavoidable if we have a rainwater catchment system with a simple drain and no nifty hydrating beds or irrigation technique. Then it is the daily march back and forth to fill it up, waiting, and waiting some more. There is the inherent danger in this method, especially if we are impatient, of underwatering. If we soak only the first few inches of soil, well, that's barely doing much good—and encouraging more surface weed growth than optimally watering your precious babies. Basically, can watering is a good method for those with soaking time on their hands and who don't nearly consider it a chore.

Many folks are trying their hand at using water more efficiently. Drip irrigation is often cited as an obvious alternative to conventional watering. As perhaps the single most impactful invention in modern agriculture, clearly it has a proven effectiveness when we think about farming innovation. Drip irrigation, while more complex to set up over a large area, is most effective for very large gardens, we dare say, farms. It is however very simple to set up a rainwater-fed, gravity-based drip irrigation line around your small garden. This will continuously water the soil around your plants. However, issues arise when we try and regulate when, where, and how much water our drip irrigation system distributes; that is, when it's not clogged. There are electronic timers that can switch systems on and off, and there are attachments that will evenly distribute drip water in multiple directions. There is much tweeking, monitoring, fiddling, and oversight required to get a drip irrigation system, large or small, to a point where one need no longer worry about watering their plants.

There is a method of watering, called wicking, which hyperwaters a small area of soil below groundlevel (the "wick") and through capillary action allows that soil wick to pull moisture upwards toward the plant roots. This is less effective for extremely large gardens or farms, and for water conservation efficiency requires some form of impermeable surface boundary. It is, however, a very good choice for small gardens, greenhouses, and even indoor, urban farming applications. Perhaps the best part of this method is that, when correctly set up, there is no human regulation required whatever. The system regulates the water in the gravel/sand beds, the soil sits on top, and the wicks pull as much water as needed to the surface. It is also a very good environment in which to germinate seed. For more information on how this method works, check out the Self-Hydrating Garden Bed kit FAQ.

Further exploring micro-climates, there are also many more methods for a total regulation of the habitat, such as in aquaponics, hydroponics, terrariums, trombes, and the list goes on. We have an ebb & flow aquaponics system at Contain Rain headquarters which works fabulously, but it does require a constant eye to be certain that the delicate balance struck is maintained. We will travel further down this road when our urban aquaponics system becomes available as a kit.

Self-Hydrating Garden Bed Kit Questions

How many barrel-beds can I put on a hydration system?

Because the system is linked to an independent cistern + float valve (how does that work?) which regulates the water level, you can add as many garden beds to the system as space will allow. As long as each is on the same atmospheric level—meaning they are all on equal ground levels with each other—the water will equalize between them (water seeks its own level). Each bed provides 6 square feet of grow space.

I don't really want to see these barrel-beds in my yard; is there any way I can bury them?

Yes. The self-hydrating system can be buried in the ground and become essentially invisible. However, this requires some additional installation work, especially (talking to Portlander's here) if they are not in a terrarium
, trombe
, or greenhouse (i.e. any covered space). If they are open to rain then an additional overflow/drainage system (e.g. a French drain, etc.) must be installed so they do not fill with rainwater during the wet season. Note that if the beds are buried, the cistern regulating the water level must also be sunk to the exact same level. Feel free to contact us anytime for more information about installing the hydrating bed system.

What kind of plants can grow in this system?

At its deepest point, the beds have a little over one foot of vertical space for roots (in covered spaces, this area can be increased by crafting a raised bed above the walls of the barrel). This is a limitation of the system as it does not have enough vertical space for some types of edible plants, such as beets and potatoes. It is entirely possible to modify this system to create deeper grow beds. Just be aware of how deep your favorite veggies must root before planting. Also note that the bottom few inches of the beds will ALWAYS be filled with water. This will most likely be fine for most plants (think hydroponics

HYDRATING BEDS SELF-INSTALLATION: Preparing your leveled space

1. Check the levels of all your barrel-beds so that they are on exactly the same atmospheric level. If your beds will be buried, level the entire dug hole. → 2. This step is critical. If you don't get this right you'll be quite sorry when you realize you must now somehow move filled beds weighing hundreds of pounds! one way to correctly level ground is to use a tube "Water Level"

HYDRATING BEDS SELF-INSTALLATION: Installing filters & infilling with sand & gravel / Installing soil wicks

1. Ideally, for two beds (12 sq ft) you will need 1 (50lb) bag of gravel and around 4 (50lb) bags of sand. The kit will provide you with a "filter" to cover the intake hole. Dump half the gravel bag near the water intake at the front of the bed. Hold the filter over the bung hole opening and spread the gravel around so the filter will stay securely in place. → 2. Take your sand and infill the rest of the barrel (holding the gravel in place). Level out the sand. → 3. Take the plastic pots provided, dig out holes with your hand, and arrange them to evenly distribute the water over the entirety of the bed(s). They should remain completely empty for now. Redistribute the displaced sand. It is ok if the pot is too short to touch the bottom of the bed, or if it sticks up slightly above the level of the sand.

HYDRATING BEDS SELF-INSTALLATION: Adjusting water level / Adding soil / Monitoring progress

1. Connect all the hoses (including the cistern) and turn on your rainwater catchment system spigot. → 2. Adjust the float valve so that water begins to fill the system. Wait until the water is at the desired level (just below the surface of the sand). [Please note, water travels very slowly through sand. Do not be fooled by the level of water in the first wicks, it will tend to be higher than the rear wicks at first, but will level out over time. The method for checking the water level requires some patience.] Be certain that the water level is UNDER the sand, or the soil will get too saturated. → 3. After you have acquired the perfect level, pull the float up to stop the flow, adjust it so that at EXACTLY that level it shuts off. Fine tuning may be done by literally bending the float's metal bar up or down. Wait an hour or so and return to make CERTAIN the water has not risen unexpectedly and is leaking out the overflow holes in the bed(s). This could potentially empty the entire contents of your rainbarrels. → 4. Add your glorious dirt. Fill and pack the wicks first, then fill the beds at least to the level of the barrel walls. You will notice that after you add dirt, the float valve will start to drip again. This is GOOD, as the soil is absorbing the water and dropping the overall level in the beds and the cistern. This will occur for two days or so... drip drip drip. Even after you're all set up, you will only ever notice the float valve dripping. This is normal. This system distributes water VERY SLOWLY (only as fast as it is absorbed by the air and plants in the system). You may have to come back and adjust the system later, but with careful setup, it would work like a charm. We had sprouts appear after only two days! Good luck!

Technical Principals of Liquids & Misc. Collection and Extraction Methods

PRINCIPAL: What is "Displacement"; and how does it work?

Archimedes discovered that any floating object displaces its own weight of fluid. Something placed within something must "displace" the molecules equal to itself. How else would it fit? The same principal applies to water flowing into a closed system occupied by air (it's not a vacuum). Where water goes in, an equal amount of air must go out. This is why most rain barrel systems must have a way of venting their air. Some methods of collecting rainwater have the air and water exchange in the same tube. When enough water enters, it creates pressure. This internal pressure forces air out (essentially 'clogging' the intake tube temporarily to let out air). The greater physical weight of the water 'falling' is enough to force its way past the air coming back out. Otherwise, the barrel would not fill. It's the same principal when you see air bubbles enter a water cooler as you are filling your cup, but in this example air is displacing water.

PRINCIPAL: So who is this guy Pascal, and why does water seek its own level; what does that even mean?

Blaise Pascal (b. 1623) was a French mathematician "of the first order". He built mechanical calculators and introduced new areas of mathematics research. His main contributions, as far as we're concerned, is his work in hydrodynamics and hydrostatics (centered on the principles of hydraulic fluids). In fact he invented the hydraulic press and the syringe. Fantastic! In the physical sciences, Pascal's law (the principle of transmission of fluid-pressure) states that "pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same." (Bloomfield, Louis (2006). How Things Work: The Physics of Everyday Life (Third Edition).) Basically, he discovered two things that explain water seeking its own level, the first was that pressure on a liquid is transferred through the liquid equally in all directions (regardless of the amount of liquid present). The second was that pressure experienced by a liquid changed at different heights (barometric, atmospheric, or air-pressure), meaning that liquid which was physically higher in space had a different amount of pressure applied to it. Because of this principal, atmospheric pressure upon liquid in a confined and connected system will seek to equalize its level. And the weirdest part is that the physical amount or proportions of liquid in the equalizing containers doesn't matter. It will ALWAYS level out to exactly the same height from the ground.

PRINCIPAL: What about gravitational pull (the water's weight); won't that be sufficient to create water pressure?

Many people have this question and hold an intuitive belief that gravity will create a significant amount of water pressure (weight) at the bottom of the barrel and in turn force the water out a spigot and hose with considerable force. We admit, it would be fantastic if this were the case. However, for as heavy as water is, the only force with consequence is the force of air (barometric pressure) pushing down on the water. The water will essentially 'fall' out of the barrel, but with only the force of falling water. It will flow so long as it is falling (flowing downward). It will not fall with any pressure behind it, and if you are holding a hose higher than the top-most level of the water, it will not flow at all. Otherwise it will spill out with hardly any force whatever. This is sometimes desirable for those who wish to drip-irrigate with their rainwater.

PRINCIPAL: What is "wicking"? How can water move upwards against gravity?

Wicking is scientifically explained using a physics principal called capillary action. "Capillary action occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces. If the diameter of [a] tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and forces of adhesion between the liquid and container act to lift the liquid." ( Basically, we've all seen a meniscus in our drinking glass. Water has a magical property of "crawing" up surfaces that are unlike itself. Wicking is (more or less) a plethora of crawling meniscus, but each moment the meniscus encounters another particle to crawl up, hence the water soaks into certain material, even vertically. Water can wick almost 12" up through soil. For more information and a guide on soil wicking see The Permaculture Research Institute's page

ALT. METHOD: I want an extraction method that has good water pressure. What about pressurizing the barrels?

We have had a few folks who bought barrels from us with the intention of pressurizing them. To us, it doesn't make sense to pressurize the system at its most dangerous point; i.e. creating a potential explosion where all the water is stored. Most systems we have seen pick another point at which to introduce 'pressure'. It takes energy to create pressure, and a COMPLETELY sealed and sound system to maintain pressure (not even tires can always maintain their pressure). Why not use the energy on demand to create water pressure when you need it, like in a pump extraction method? Or if you must create and maintain pressure in the system, most we've seen use an air compressor attached to the system. In short, we do not recommend unnecessarily pressurizing the water barrels themselves.
See more FAQ's