Introduction: Rainwater Harvesting: Rain Barrel DIY

Rain water collection. Nature's most fundamentally important resource for human habitation -- the earth purifies it from all sorts of sources through the evaporation process, transports it all around the globe, then drops it from the heavens for us to drink, water our crops, bathe and swim, among myriad other uses. Modern humans have found lots of ways to squander precious fresh water, but this easy, inexpensive solution captures an potentially lost resource for effective reuse. How much more green could an Instructable be?

Rain barrels capture rainwater otherwise lost through the downspout to use for watering your garden between rains. But rainwater harvesting has lots of benefits beyond simply watering your garden. It's also good Green Tech. It's a low-cost solution for a number of potential issues:
  • It reduces stormwater runoff created by the roof of your house
  • It can reduce property drainage problems
  • It contributes to a LEED Green Building rating
A rain barrel collection system is simple and easy to maintain, Rainwater is better for gardens and landscape plants than municipal water because it doesn't contain chlorine, it's relatively clean and it's absolutely free. It is also a system that can be expanded easily to create additional rainwater storage, and it can be dismantled and relocated if necessary.

This instructable documents how to construct a simple rain barrel used to collect rainwater runoff from a downspout. It uses readily available parts found at your local hardware or plumbing supply store, and it uses basic tools found in many tool kits. For those tools you don't have, they're easy to source and inexpensive.

Step 1: Parts List and Materials

The rain barrel starts with a food-grade barrel, modified to accept and store rainwater run-off, discharge excess rainwater once the barrel is filled to capacity, and dispense rainwater for watering the garden or for whatever use you find for captured rainwater.

Note: It is not recommended to use captured rainwater for drinking, but the food-grade component ensures that the barrel has not held contents that could damage the water supply or plants, or be absorbed by plants and then ingested when those plants are eaten.

I use it for the following:
  • Water the garden
  • Refill the toilet toilet tank after flushing
  • Various household construction and cleaning uses
The components cost between as little as $25 to more than $60 depending on what you're willing to spend. Including the Lee Valley components below, the total came to about $40 and the barrel was another $20. (The optional quick-connect coupling would add another $10.) You may be able to source less expensive components. 

There are various acronyms used with plumbing fittings, and I will list the ones I used here:
  • NPT -- National Pipe Thread
  • GHT -- Garden Hose Thread
  • HB -- Hose Barb

Components for the rain barrel (parts I used and approximate cost in parentheses):
  • Food-grade watertight barrel (220 liter Greek pickle barrel, $20)
    My local hardware store happens to sell used food-grade barrels during the summer.
  • Screen to filter incoming rainwater (3" kitchen sink strainer, $1)
  • Overflow fitting (Right-angle 3/4" inner diameter 1-1/2" male NPT to 1" HB fitting, $1.75)
  • Overflow hose (1-1/4' flexible hose, 6 ft, $3)
  • Bulkhead fitting (Bulkhead fitting, 1-5/8" outside diameter, NPT female threads to accept a standard 3/4" spigot, $8)
  • Nipple to connect bulkhead fitting to shut-off valve (3/4" male NPT to 3/4" male GHT, $1)
  • shut-off valve (Lee Valley Straight shut-off valve, $13)
  • Hose union gasket (Lee Valley O-ring washer, 10 for $3.25) 
  • Optional: quick-connect fitting (Lee Valley Brass Quick Coupler, $10)
Dry fit all components once collected to make sure all threads match and everything fits as expected. 

For the base of the barrel, I used a couple of cinder blocks and a piece of flat blue stone I had in the yard. This makes filling watering cans a lot easier. The higher you're willing to put the barrel, the more water pressure you can achieve. 

Step 2: Tools for the Job

I made my first rain barrel using a Dremel tool for cutting the holes, but I found that the results were not very precise. I purchased a 10-piece hole saw from Harbor Freight for about $8 and it made the job significantly easier. The remaining tools I had in my collection already. The only really unusual tool is the Clamp Tite tool I used for fabricating the hose clamp using stainless steel locking wire. You could use a simple screw/band hose clamp instead.

Tools required:
  • Drill
  • Hole saw
    • 3" cutter
    • 2" cutter
    • 1-3/8" cutter
  • Marker
  • Teflon tape
  • Silicone sealant
  • Pipe wrench
  • Slip-joint pliers

Optional tools:
  • Clamp Tite clamp tool
  • Stainless steel locking wire
  • Wire cutters

Step 3: Component Details

The bulkhead fitting is an important component. It provides a fitting that can withstand the pressure of gallons of water trying to exit the barrel through the big hole you're about to cut near the bottom. The fitting also provides a union point for the valve. I used a fitting that fits nicely in a 2" hole, and has a rubber gasket that is compressed against the inside wall of the hole with the poly nut threaded on the fitting from the outside.

The bulkhead fitting uses a left-hand thread for the nut. This allows the bulkhead fitting to stay tight after installation when installing the right-hand thread valve assembly. 

The valve assembly consists of a nipple that forms the union between the bulkhead fitting and the valve. The valve used is a 3/4" ball valve. Rather than a pin valve, when fully open, this valve has no obstruction to water flow. It is also allows visible inspection of whether the valve is open or closed simply by observing the position of the handle. It costs a little more, but performance is a big value point for me, so I splurged.

I have also depicted a brass quick-connect coupling in the assembly. I also have one on my hose spigot coming from the house water supply, so I can easily and quickly disconnect the garden hose from the house and attach it to the rain barrel. This coupling is also great for hose ends, to allow for quick changes among nozzles, sprinklers, watering wands, etc. Again, performance is worth the added expense, in my opinion.

Step 4: Cut the Valve Hole

When locating the hole for the bulkhead fitting, sight it a little up from the bottom of the barrel, so sediment will settle below the level of the valve and drawn water will be clear. This also allows the valve fitting to project more horizontally from the barrel.

Use the 2" cutter.

Mark the center and start the pilot hole of the hole saw on that mark. 

Step 5: Cut the Top Hole

Use the center mark in the top as the mark for the hole saw.

Use the 3" cutter and cut the hole to accept the strainer.

Step 6: Cut the Overflow Hole

The overflow hole will provide an exit for excess water once the barrel has reached capacity.

Mark the center, use the 1-3/8" cutter and cut the overflow hole.

This hole is a little undersized to provide purchase for the threads of the right-angle fitting. 

Step 7: Assemble the Valve

Install the bulkhead fitting by removing the nut and friction washer, then passing the fitting with the rubber gasket attached from the inside of the barrel through to the outside. Install the friction washer then thread on the nut. Finger tighten the fitting.

Note: The left-hand threads of the bulkhead fitting will provide counter-rotation when tightening the right-hand threaded valve assembly into the fitting.

Attach the nipple to the valve, applying Teflon tape to the male threads. Use slip-joint pliers to create a tight union.

Apply Teflon tape to the male threads and join the valve assembly to the bulkhead fitting. apply the pipe wrench to the bulkhead fitting washer and tighten the valve assembly. Tighten the valve assembly firmly and rotate the valve handle to the top. Then use the pipe wrench to tighten the bulkhead fitting.

It's easy to over-tighten this connection and deform and possibly weaken or damage the barrel, so wait until the barrel is filling with water to determine how much torque is needed to keep water from leaking through this joint. Adjust the tightness of this fitting to be just tight enough to keep water in when the barrel is full. Hold the valve in the desired position and turn the large nut with the pipe wrench. Remember, left-hand threads tighten the opposite direction! The nut on my fitting actually depicts the direction to rotate (counterclockwise) to tighten.

Step 8: Assemble the Overflow

The hose I had was slightly larger than the fitting, so it required a hose clamp. A common screw/band hose clamp is easy to find, but they can be bulky and I have seen them rust over time. In this case, I used a hose clamp made with a Clamp Tite tool. Here is an Instructable of mine that describes the process in detail.

Once the fitting is in place, seal the seam between the fitting and the barrel inside and out with silicone sealant to keep excess water from seeping down the side of the barrel instead of exiting through the hose.

Step 9: Position the Barrel, and Put It to Use!

Locate the rain barrel near a downspout. Raise the barrel up off the ground to permit easier filling of watering cans, and to provide a little more pressure from gravity. I have also tried to choose locations in the yard that are higher than the garden so gravity can feed the watering process instead of having to lug watering cans form barrel to garden. 

I used a couple of cinder blocks and a piece of flat bluestone I had in the yard. Whatever you use, make sure it can hold up to a rain barrel filled with water. 200 liters of water weighs 440 pounds, so consider this when establishing a base for the rain barrel.

With the quick-connect coupling on the valve, this allows for easy connection of a short hose for filling watering cans beside the barrel, or a quick switch to the garden hose for reaching out into the yard direct from the barrel.

The fourth image in this step is a previous barrel I have installed beside the front door. It shows the downspout diverted using a flexible downspout to the top of the barrel. The outflow tube continues into which the drain that the downspout used to connect, completing the circuit with the reservoir that is the rain barrel in between. The cable keeps the flexible downspout from falling off the top of the barrel.

Step 10: Wrap-up

Rain barrels are a great way to reclaim an otherwise lost resource. This barrel can be fabricated for around $50, and will last for years. We have had a lot of luck with these barrels. I have made barrels for friends and family. We have found that we can capture and reuse multiple hundreds of gallons of rain water during a typical summer season. That means less runoff into local streams and rivers, less water around the foundation, lower water bills, and the right type of water for the right purpose. While rain water is not suitable for drinking, there's no reason to use treated municipal water on flowers and plants if rain water is readily at hand. Rain water is fine for toilet tanks and other gray water uses. 

One note for those who live in cold winter climates: Remove the barrel from the downspout when chance of freezing exists. Water expands 9-10% when it changes to ice, so it will ruin a perfectly good rain barrel if it gets a chance. Be sure to empty the barrel and put it away, out of the sun, during freezing seasons.