DIY Rain Catchment with 55 Gallon Barrels

I built a small, experimental water catchment system for the north side of my garage using 55 gallon barrels and pvc pipe.  If it works, it has the capability of holding around 150 gallons.  I will need to drain it before each new rain event or it will likely overflow.

The interesting element of this project is the use of upside down barrels.  The piping is introduced into the female bung screw holes with male adapters. The barrels are flipped over so the top is underneath the system.

The standard 55 gallon barrel has a bung cap that screws into threads in the barrel.  The key to this system is the male pvc pipe adapter and slip.  The entire system is mostly closed with minimal drilling into the barrel except for two places--the ingress and egress overflow points of the system. Here, for example, I created the small catchment system for our garage roof. My north-edge plastic gutters drain into the first barrel which gravity fills through the pvc piping into the other barrels.  Here is how I made the system using mostly 2 inch pvc parts.

First, remove the bung nut.  You can then insert the male threaded pvc adapter with slip into the hole and screw it down.  I used plumbing tape over the threads of the adapter to discourage leaks. This adapter creates a nice seal and the slip piece allows us to attach the other plumbing.

Cut 4-inch short pieces of pvc pipe for the top of each barrel.  Cut the pieces of pipe at a 90 degree angle, smoothly cut.  Use pvc primer and solvent to connect and set up a good seal between the pipe and adapter. When done, you have an adapter screwed into the bung hole with a short piece of pipe sticking up out of it.

Connect your other fittings to the end of the pipe that emerges from the top of the adapter. For this three-barrel system, from left to right, I installed one 90 degree and two T-joints.  You need more T-joints if you want to link additional barrels.

You will set the barrels up on something solid like concrete blocks.  Level the blocks out.  You should aim to place each barrel slightly higher so that the last barrel is the highest.  However, you do not want the last barrel so high that your system overflows at the ingress point. If you get this right, gravity forces the water to fill most of barrels full before water overflows from the third barrel's overflow pipe.  I will get to that in a bit.

Flip all the barrels upside down and organize them on the blocks so the pipe joints are lined up.  Measure and cut pieces of pvc pipe so each barrel is linked underneath by 2 inch pvc pipe.  Use the primer/solvent to set up a good seal for the pvc pipe between each joint.

The last barrel T-joint has a 3/4 inch bushing at the end.  Into this bushing, one can screw a faucet.  This allows you to drain the barrels in times of drought.

You can improve on my design by extending pvc pipe from the last T-joint before installing the bushing. You  might need a 2x2 coupling to do this.  The design improvement will give you more space to make your drain hose connection.

The top of the last barrel must have an overflow outlet.  This is a pretty small system. In a heavy rain, a roof the size of my garage (around 500 square feet) can fill the three little barrels in about 15 minutes.

For the ingress hole in the first barrel, use a 2 3/8 hole cutting bit on your drill to cut a hole in the top of the upside-down barrel.  Attach a 18 inch  pipe to a 2 x 4 inch coupling.  Stick the pipe end down the hole.  It should fit pretty snuggly.  The 4" coupling is big enough so your gutter downspout will fit into the top of the coupling.

The overflow system is similarly engineered.  Cut the 2 3/8 inch hole near the top outside end of your last upside down barrel.  My current overflow system is still a work in progress.  I will update this later when I get it figured out better.

For now, I temporarily rigged my overflow pipe with a 6 inch piece of pvc pipe connected to a 3x2 coupling.  I connected the pipe to the coupling and stuck it into the hole.  The overflow comes out the coupling and spills onto a brick next to the barrel.  However, the seal and overflow system is inadequate.  Moreover, the spill does not go where I want it to go.

I will figure out how I can put some kind of rubber washer between the coupling and the barrel so leakage will be reduced.  Unless I figure out something better, I will connect a 3" pipe, a 90 degree joint, 3" pipe, 3x2 coupling, 2" pipe, 90 degree joint, 2" pipe, 2 x 3/4 bushing, drain hose.

Eventually, my plan will connect my drain pipe together using a hose Y connection.  The drain hose goes down hill to a swale at the top of our western planned orchard.

Watch this post for updates when I figure out the parts for the overflow and drainage elements.

The parts for the project (all 2 inch pvc) were as follows:

• Barrel Plumbing Connections

1. 2" pipe; 
2. 3x male threaded adapters and slips;
3. 90 degree joint;
4. 2x T joints;
5. 2 inch to 3/4 inch female bushing;
6. 3/4 inch Faucet
7. drain hose;

• Ingress Connection

1. 2 x 4 inch coupling;
2. 2" pipe

• Overflow Connection

1. 2 inch pvc pipe
2. 3 inch pvc pipe
3. 2 x 3 inch coupling
4. 3 inch 90 degree joint
5. 3 x 2 coupling
6. 90 degree joint
7. 2 x 3/4 female bushing 
8. 3/4 inch faucet;
9. drain hose