How to Build a Rain Barrel

How To Build a Rain Barrel

Rain barrels help reduce stormwater runoff and can reduce your potable water consumption by providing a free source of water for landscape irrigation purposes. This article describes how to build your own rain barrel through a process that takes only an hour or so, using common materials that you can get for less than $40, and producing a rain barrel that I have found works great.  Here is what you need to build it:

  • A food grade plastic drum or tank.  I usually have no problem finding used, food grade, 55 gallon drums for $20 or less.
  • A drill.
  • Two hole saws (or large drill bits).
  • Two square feet of hardware cloth.
  • One square foot of mesh screen.
  • A reciprocating saw, keyhole saw, or utility knife with a sharp blade.
  • One or more brass hose bibs, either ½” or ¾”.
  • A couple of PVC fittings (more later).
  • A downspout adapter to get the water to the barrel.

Step 1: The Overflow

PVC 90 degree elbow and threaded male adapter with a 2 1/4" hole saw sitting on top.

The first and most important part of building the rain barrel is the overflow.  It is important because it will prevent you from creating a water problem next to the foundation of your house where you once had a perfectly functional gutter.  This is also the feature of this rain barrel design that makes it better than any other rain barrel I have seen, because I use a 2” PVC overflow instead of a small fitting connected to a garden hose.  In my experience, a heavy rain can easily overwhelm a smaller overflow.

This is where the two PVC fittings come in, or you may want more if you plan to create a more elaborate set-up.  The two fittings you’ll need are a threaded male adapter that has threads on one end and a slip connection on the other end, and a 90 degree elbow.  They are both shown, glued together, in the picture on the right.

This step simply involves cutting a hole in the side of the rain barrel with a drill and hole saw.  Choose a hole saw that has an outside diameter about 1/16 or 1/8 of an inch smaller that the threads of the male adapter, as shown here.  In this case, the male adapter is a 2” fitting, and the hole saw is a 2 ¼” hole saw.  You need to drill the hole in the side of the plastic drum just a few inches below the top.  The hole saw, though probably made to cut wood or soft metals, will handle the plastic just fine.

Constructing the overflow.

Once you have drilled the hole, screw the male adapter into the hole by applying even pressure and twisting it while making sure that the fitting stays square to the barrel.  The threads of the adapter will thread their way into the softer plastic of the barrel, and you will soon see them disappear as you screw the adapter into the barrel.  Though it may not be necessary, a little bit of silicone plumber’s tape or silicone caulk will ensure a water-tight seal.  At this point, you should direct the overflow to wherever the downspout used to go, or perhaps to a more appropriate place, using PVC or just about any other sort of pipe or some means of directing the flow, as long as you get it a decent distance away from your house.

Step 2: The Hose Bib

A brass hose bib installed on the barrel.

The rain barrel pictured here has two ½” brass hose bibs to which you can attach a regular garden hose.  They can be installed on the plastic barrel in the same manner as the overflow, by drilling a hole slightly smaller than the brass threads and screwing it in with even pressure.  Once again, silicone caulk or silicone tape can be used to stop any drips.  I suggest keeping the hose bib at least about five inches up from the bottom of the barrel, as you will almost certainly see a build-up of tree litter, pollen, and dust in the barrel that could clog the hose bib as they settle to the bottom of the barrel.  See “Step 4” for how to get rid of this muck.

Step 3: The Inflow

The 3-layer cap and self-tapping screws.

This is the step where you will create a way for the rainwater to get into the barrel.  Depending on the type of barrel you have to work with, there will almost certainly be a place on top of the barrel large enough to cut a roughly 8” diameter hole.  This can be done with a number of different saws or cutting utensils.  A reciprocating saw or a keyhole saw is probably the easiest, but a sharp razor blade in a utility knife will also do the trick, just BE CAREFUL!  I have seen rain barrels made by cutting the whole top off of the barrel, but I suggest just cutting a hole in the top which will leave the barrel more intact, stable, and re-usable.After cutting the hole in the top of the barrel, cover the hole with a three-layer cap: two pieces of ¼” hardware cloth sandwiched around 1 layer of mesh window screen.  The hardware cloth will make this cap durable and help it stand up to the rushing water, and the screen will prevent mosquitoes from entering the barrel.  Allow the 3-layer cap to overlap the edges of the hole about 1 inch or more all the way around, and attach it to the barrel using ¾” self-tapping sheet metal or gutter screws as shown here.

In addition to keeping mosquitoes out of your rain barrel, the cap will serve as a filter for some of the larger tree litter that may have made its way into your gutters.  Depending on how many trees are close to your house, you will have to clean this debris off the top of the filter regularly, as discussed in “Step 4”.

Step 4: Use and Maintenance

A 50 gallon rain barrel will fill up pretty quickly unless there is a very small amount of roof space feeding water to it.  Therefore, in order to get the most out of it, you should water with it frequently.  I do not recommend using the water from the rain barrel to water your vegetables or other edible plants, unless you are sure that your roof will not leach any chemicals into the run-off.  On the other hand, I have not had any trouble or negative effects on my other plants from several years of watering with the water that comes off of my asphalt shingle roof.  In fact, the only “problem” that I have is that the water tends to be a little bit stinky from the tree litter decomposing and the algae growth.

As mentioned earlier, it will be necessary to clean the muck out of the bottom of the barrel once in a while.  I have a lot of trees around my house, and I can still usually get by with cleaning out completely once a year, and just cleaning the stuff off of the top of the cap about once a month.  In any case, the screws used to secure the 3-layer cap to the top of the barrel can simply be removed, allowing access to the inside of the barrel.  Once this is done, my favorite tool to clean the barrel is a large sponge zip-tied to the end of a 4-foot stick.  I just scrub it out, rinse, and that’s all.  Just remember that if this process involves rolling the barrel around on the ground, be careful not to break the hose bib or the overflow loose from the barrel.  When you are finished, just replace the cap and put the barrel back into use.

A rain barrel made from an 80-gallon olive barrel