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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    57 Discussions


    Question 3 months ago

    Just found your project. Appreciate all the tips including the sight gauge and manifold setup. I would think the roof-wash system would be good to avoid filling the initial filter screen with a lot of particles or is that a non-issue?
    You said that the caps are left off the 2 extra tanks but I assume they do have screens?
    "every 2.31 feet of water (head/drop) creates 1 psi." So you should be getting 1 to 3 psi of water pressure (depending if tanks are full vs empty). I'm guessing that even 1 psi is enough pressure for a soaker hose w/o adding a pump?

    1 answer

    Reply 3 months ago

    You certainly could add a roof-wash system if you wanted. Particles getting in just hasn't been an issue with this system. (I will say that metal roofs are ideal for rain collection!)
    The other tanks are screened, so they are at atmospheric pressure, but can't get bugs/grit/ick or anything else in there.
    This is a pretty low pressure system. If you want a higher pressure system, raise your storage tanks as high as possible.

    This system was just designed for plain watering of some garden plants with just a regular garden hose. I took a quick look at the pressure requirements for several types of drip tape, drip hose, poly tube with emitters, etc. They all look like they need a fair amount of pressure. The lowest I saw listed was 10 psi, with some types of irrigation controls needing up to 25-30 psi.

    If you want to use some sort of automated irrigation controls, you would need higher pressure. That might be possible just by getting the storage tanks higher up. You COULD use a pump to get water up to the tank, and allow the tank to provide natural water pressure. Otherwise, you could also add additional equipment such as a pump, pressure tank, check valves, but at that point, it's almost like you are just redesigning a home water system. In our case, we just wanted something simple to use for watering the garden in the back yard using rain-water.

    Simple is best, unless you have some real particular limitations, such as being off-grid, can't drill a well, etc.

    Good luck on your rainwater project!


    2 years ago

    I'm late to the party here. Love this instructable. I never knew about these containers till I saw this post. Unfortunately up here,those containers go for a pretty penny, 150-250 for food grade. Hope I can find cheaper. Thanks for posting.


    3 years ago

    At some states, water collection is illegal regardless of whether or not the storage container belongs to you. Even though rainwater is free but to collect it and eventually using it for your own personal benefits seems to be an issue to the authorities I suppose. Sad, but definitely true.


    4 years ago on Introduction

    I just got my hands on one of these ibc containers for $20. Great instructable! Going to use your plan for the filter/cover mod!


    5 years ago on Introduction

    Low maintenance cheap filters *could* be a way to reclaim the expenses of a high maintenance expensive GF. Marriage would provide a lifetime supply of disposable items like that.


    5 years ago on Introduction

    Just make sure that the IBC was not used in harsh chemical usage. I made them for years and the 55 gallon drums. Your best bet is to get them from someone that had food grade usage and the IBC was made for food grade usage. Also if you can find out if it was made with Ultra Violet additives. (helps keep the algie out)

    1 reply

    Reply 5 years ago on Introduction

    True, I try to avoid harsh chemicals in all ways I can. In this case, picked up these IBCs from a beverage bottling company. They originally contained corn syrup. We simply washed the containers out well.


    5 years ago on Introduction

    I've got a similar system at my house which takes water from my garage and man cave roof. I've not boxed them in yet. It's on the to do list. Currently they're covered in winter squash, so adequately shaded!


    6 years ago on Introduction

    I have something similar on my carport for the past 10 years or so.

    What happens to the overflow when your tank is full? I had to add a 25mm overflow hose down to the drain, so that the barrel doesn't flood out the top.

    How to get pressure? Your tank is almost at ground level so there's not a lot of differential. Mine's about 500mm off the ground, so can still push water down a hose. Could use a pump to generate pressure.

    Our need for water drops right off in winter - I'm tempted to just take the tank out of the line to stop collecting roof dirt.

    Finally green shit - it grows. If you do box in your tank then make sure there's a way to get it back out for a scrub.

    2 replies

    Reply 6 years ago on Introduction

    I was reading this and thinking the same thing. Worse thing to happen would be the overflow is improperly directed to a wash or your septic tank area.


    Reply 6 years ago on Introduction

    The tank is on the highest point on the property, and is on top of a rock garden, which gives it just a little more height. Instead of being on a stand, the tank just happens to be higher than everything that it will water.

    The tank doesn't have an overflow yet. (We have been in a major drought, so it hasn't been an issue yet....)

    The plan is that we will add an overflow right at the top where the water inlet is. We might design a "roof-wash" device there as well.


    6 years ago on Introduction

    I am amazed that any state in this country COULD make it illegal to collect rainwater.
    It falls from the sky, no one owns it.
    If it lands on my property, I should be able to collect it.
    I've never heard of anything so ridiculous in my life; I'm really pissed off just reading about this.
    I don't know if it's illegal in my state and I don't care; people have to draw a line somewhere and if the state wants to send me to jail, let's go.

    Sorry for the rant; great instructable by the way.

    6 replies
    Bosun Rickgjm

    Reply 6 years ago on Introduction

    If it falls from the sky, or is ambient to the earth, it is a gift from God. Obama & Co. apparently don't believe in God, thus making it illegal to own rain or air. What does this mean for the solar collecting community?


    Reply 6 years ago on Introduction

    Around here, (Indiana) cities want you to do whatever you can to capture or use rainwater. We have a problem with storm water and the overall waste water processing system can't keep up in heavy storms.


    Reply 6 years ago on Introduction

    Milwaukee, Wisconsin also has a huge problem with the sewer system. Any time there's a big rain-storm, it ends up causing untreated sewage to go right out into Lake Michigan.

    If everyone collected rainwater, it would help with the problem.


    Reply 6 years ago on Introduction

    Not that new a concept actually, some countries in Europe have been taxing for rainwater for a long time, all based on square footage of property.


    Reply 6 years ago on Introduction

    Gjm- This is a pretty recent news story, relevant to the law. Don't get me wrong, I totally agree with you, but it's crazy what the government can do. I just hope I'm not stealing air from the state when I run my air compressor!

    Great Instructable by the way!


    6 years ago on Step 5

    How do you take care of mosquito's?