Introduction: DIY 275 Gallon Rainwater Collection

About: Ordinary guy with no special skills, just trying to change the world one backyard invention at a time. See more at: On Twitter - @300MPGBen and at
I recently helped my father install a 275 gallon rainwater collection system.

The system is based on an industrial 275 gallon container, known as an IBC. You can buy them used, or if you really look around, you can even find them for free. One problem with typical rain-barrels is that they can only collect 55 gallons. This rain storage container collects FIVE times that volume, while not taking up all that much more space than a single rain-barrel.

In my area, you can buy used IBCs through Craigslist for about $85 each. Those come with a metal cage around them that allows them to be stacked.

Instead of buying them, I found a local bottler who throws them out, because they are plastic containers WITHOUT the metal cages. These containers come to the bottler full of 275 gallons of high-fructose corn syrup. I got several containers from them for free, for just the elbow grease of going to pick them up. Some were wrapped in heavy cardboard. I recycled the cardboard into a clubhouse for my little girl.

After washing the container out well, it is ready to be repurposed for rainwater collection. I really like the irony of using GMO corn syrup containers to recycle into a conservation project!

Besides the water container, this project requires other materials, including:
  • Misc wood to build a simple pallet or platform
  • Garden hose spigot and hardware
  • Gutter screen and fiberglass bug screen
  • Gutters, downspouts, and elbows
  • Silicon or other appropriate caulk or sealant
In our case, nearly all the materials were already on-hand, reusing old components, and recycling and repurposing materials. Total out of pocket expenses were under $20.

Beyond the typical DIY and handyman tools, you will need:
Tin snips, utility knife, pop-rivetter and rivets, sheet metal screws, and related aluminum metal-working tools and skills.

Lets get started.

EDIT: July 2013, we updated this to TRIPLE the capacity, raised the containers, and made them look really nice. See the update at:

Step 1: Locating the Storage Tank

The first thing you need to do is decide where you want the container to go.

It needs to be located near the building you want to collect rainwater from, and it also needed to be elevated if you want it to work on gravity flow.

In this case, the building is a 100 year-old barn that was remodeled into a home office. The roof is a fair amount of collection area, and the building is on the top of a hillside - it's basically the highest point on the property. Because of that, the container was NOT put on any kind of a stand.

There was a small rock garden right outside the barn that was slightly elevated. We leveled off a 4'x4' area there for the tank.

That corner of the barn is also right where the downspout from one side of the roof is. That will make it a short distance to route the downspout to the tank.

Next, we built a pallet out of scrap pressure-treated wood for the container to go on. This gives the container a solid base and gets it up just a little higher, making it easier to access the garden hose spigot we will add.

The front of the pallet has a notch around the drain port, which will make it easier to access the garden hose spigot later.

Step 2: Modifying the Tank Fill Port Cap

Next, we need to modify the inlet of the tank so that we can get the rainwater in, without letting in leaves or anything else.

The fill port in the top of the tank is a 6" screw-on cap. Just removing the cap leaves a nice big hole to let things in, but even animals could get in there if you did that!

So, we decided to modify the cap to include a screen, make it self-cleaning, and keep out mosquitos.

First, we notched out the edge of a 4" PVC pipe cap wide enough for a gutter downspout using a jigsaw.

Next, we centered the 4" pipe cap on top of the 6" cover. We then drilled holes around the inside edge so we could use pop rivets to connect the two. After trying a rivet, we realized the rivets we had were EXACTLY the wrong length, so we used some sheet metal screws instead. 

Then we drilled through both the pipe cap and cover with a 3" hole-saw. That kept a half-inch lip all the way around the inside of the pipe cap for the screws that held both parts together, AND as a place for our "Coarse-Filter" to rest.

To keep large items out of the storage tank, we needed some sort of screen. Since we had some aluminum "gutter-guard" around, we traced the 4" pipe cap onto it with a marker, and the cut the inside of the line with a tin snips. We then had an aluminum circle that fit inside the pipe cap, and would rest on the ledge inside. I friction-fit in place just fine, but you could add some sealant to make it more permanent if you wanted.

Lastly, we cut some scrap fiberglass bug screen to a little bigger than the cap. We simply laid the screen over the 6" hole, and then screwed the cap back on top right over it. That way, there is both the aluminum coarse filter to keep leaves out and screen to keep out mosquitos.

Step 3: Converting the Drain to Garden Hose Connection

The 275 gallon IBC features a 2" drain port on the front bottom. It has a cheap plastic ball shut-off valve, and a 2" plastic cap that gets screwed on to keep it from leaking.

Rather than use a number of PVC pipe adapters to get down to a garden hose, we reused the 2" cap and some spare plumbing parts we had kicking around.

To start with, we had a brass spigot with 3/4" NPT (National Pipe Thread) male connection on it. Standard threaded pipe is tapered, so the farther you screw it in, the bigger it gets. This helps make solid, water-tight connections.

We drilled a 3/4" hole through the center of the 2" drain cap.

Next, we stuck the pipe end of the brass spigot through the cap, added some sealant at the joint, and then threaded on a nut from the back side. Since the hole was the right size to start with, the sealant and tightened nut made a solid connection on the cap.

We then headed back outside. Using plumbers putty (you could also use teflon tape) we threaded the drain cover with spigot onto the drain.

We decided to have the brass spigot rotated clockwise part-way, because the open big drain valve made it harder to grab the knob on the spigot.

Then we connected a garden hose, ran it down-hill, and tested our flow from the rainwater collection system.

Step 4: Gutter Work

Now for the tough part - modifying the gutters and routing them to the storage container.

For the gutter closest to the rain container, it was pretty straight-forward. We cut the downspout a few feet above the container, and then set the cut-off piece to the side for later use.

We also wanted to collect all the water from the other side of the roof as well. To do that, we added two elbows to snake the downspout around the back of the barn, and then a long section of angled downspout sloping downward, towards the rain container.

We had to figure out the best way to connect both gutter downspouts together to combine the water going to the rain container. After a little thought, we decided that the best way to do it was to use another short piece of gutter. Not only did we need to combine both downspouts, but we also needed to move the water sideways a couple of feet and then send it to the IBC. A short piece of open gutter could accept both downspouts AND extend to the IBC tank. It would then have an elbow and short downspout going directly to the the fill port on top of the tank.

I had never worked on any gutters before, so I got a lesson on working with aluminum, sealing it, and in the mind-set of how water flows. About half an hour later, I had created my very first custom gutter. I then attached it to the wall of the barn with some long screws, and a slight slope towards the rain container.

We now had a rain collection system - two gutters, whose downspouts combined into a short gutter, which lead directly to the rainwater storage.

Step 5: Learning Experiences and Future Improvements.

A little back of the hand math, ball-parking the size of the roof compared to the volume of the container, told us that one inch of rain would be enough to fill the whole container. Sure enough, when we finally did get some rain, less than an inch filled it most of the way up!

After we installed the gutter modifications, we cleaned the gutters real well. This is a typical asphalt shingle roof, and the grit from the shingles DOES come off. We flooded the gutters, and rinsed the entire roof, with the output of the gutters diverted from the storage tank. Next, we are adding gutter-guard screens to the full length of both gutters, as well as our short section that combines both downspouts.

Although a metal roof is ideal for rainwater collection, this building was re-roofed not long ago with the asphalt shingles. The water will be used for general irrigation, and not for watering animals or human consumption.

Because of the angle and direction that the downspout goes into container, it makes a good point to add an extra section of downspout to just "overshoot" the storage tank. For example, that's what we did when we washed the roof and cleaned the gutters. Some people use a "roof-wash" system - that's a way to DIVERT water away from your storage container at the beginning of a rain storm, so that the water washes the roof clean, once it's clean, the system then allows water to go to the storage container. This is often accomplished with a spring-loaded bucket contraption that uses the weight of the water filling a bucket to then connect the diverter to the water storage container.

If we want to add a "roof-wash" diversion device to the system, we will most likely add it right before the tank's fill port.

One thing that I learned the hard way on this project... DON'T fill the tank all the way up with water for experimenting! When I was putting up the short section of gutter, I had to work around the tank. I didn't have a good place to lean the ladder, and I was working at odd angles with the screw driver to put up the gutter. If I had just left the tank empty, we could have simply moved it out of the way!

After the first big storm and some hot weather, we noticed that the shape of the tank bulged and distorted a bit. It's not that it was going to rupture or anything - mostly it just looked really bad. Many of these tanks come "caged", which helps them keep their shape and makes it possible to stack them when full in warehouses. Since this container isn't caged, we are thinking right now that we will box it in with wood, to not only help it keep it's shape, but also make it match the barn and chicken coop. The wood boxing could also keep out sunlight, to prevent algae growth.

This is the first LARGE water collection system I have worked on. It is slightly experimental, and I expect that we will add some improvements in the future. In the mean time, I hope that our work on this system gives you some great ideas on how you might want to collect your own rainwater!

UPDATE: Early Summer 2013
We are increasing the size of the system to TRIPLE the original capacity and building it on a raised platform for better water pressure and gravity flow.

Besides tripling the size, the tanks are boxed-in, making them look nice and keeping sunlight out. A site-guage is added on the side to tell how much water there is, and an outdoor wash tub was added to the end. The drain of that washtub gravity feeds to the waterfall and pond just to the side.
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