DIY Rain Barrel from a 55-Gallon Barrel (Almost Free)

Last August I paid to water my garden for six weeks straight while water literally ran off my shed roof into the gravel below. It took me until the following spring to do anything about it. I’m not proud of that, but it’s very on-brand for me. Building a DIY rain barrel turned out to be one of the easiest fixes I’ve ever put off.

A 55-gallon rain barrel built from a food-grade barrel is one of the highest-return projects I’ve done in this garden. The barrel itself is often free or nearly free, the parts are cheap, and a single summer storm can fill the whole thing before you’ve finished your coffee. Let me walk through how I built mine.

Finding a Free or Cheap Barrel

Food-grade 55-gallon barrels are everywhere if you know where to look. Car washes, food manufacturers, farms, and breweries go through them constantly. Post on a local community board or check the free section of a classifieds site. I picked mine up from a car wash for nothing. It previously held soap concentrate, which rinsed out fine. Avoid anything that held chemicals, pesticides, or petroleum. Just ask what was in it before you load it.

If you can’t find a free one, used food-grade barrels usually run somewhere under $30 at farm supply places or through secondhand listings. Still a solid deal.

What You’ll Need

• Food-grade 55-gallon barrel (ideally with a sealed lid)
• Brass or plastic spigot with a threaded fitting (the kind made for barrels specifically)
• Overflow fitting or a short length of PVC pipe and elbow
• Fine mesh screen or fiberglass window screen material
• Waterproof silicone sealant or plumber’s tape
• A hole saw or a sharp spade bit that matches your fittings
• Cinder blocks or a short wooden platform to raise the barrel

Total parts cost runs somewhere in the $20 to $40 range depending on what you have lying around. I already had the silicone and the drill bits, so I think I spent under $25. Barrel was free. You do the math. (That’s the fun part.)

Building It: Step by Step

Step 1: Raise the Barrel

Set your barrel on cinder blocks or a sturdy platform before you start drilling. You want at least 12 inches of clearance underneath so a watering can or bucket actually fits under the spigot. Gravity is free pressure. The higher you go, the better the flow.

Step 2: Install the Spigot

Drill your spigot hole about 3-4 inches from the bottom of the barrel. Not at the very bottom or you’ll never get all the water out, but low enough to drain most of it. Thread the spigot through, wrap the threads with plumber’s tape, and snug the nut down from the inside. Run a bead of silicone around the outside and let it cure for a full 24 hours before you trust it. I rushed this step the first time. My shoes got wet. Learn from me.

Step 3: Cut the Overflow

Near the top of the barrel, maybe 3-4 inches below the lid, drill a hole and fit your overflow pipe. This is where excess water goes when the barrel fills. Point it away from your foundation. A short PVC elbow directed toward your garden bed or a soaker zone works great. You can also run a hose from here to a second barrel if you want to get ambitious. I am not that ambitious.

Step 4: Screen the Inlet

This is the part people skip and then regret. Cut an opening in the lid (or use the existing bung hole) where your downspout will flow in. Cover it with a double layer of fiberglass window screen and secure it with a hose clamp or a ring of waterproof tape. Mosquitoes will absolutely breed in standing water. The screen stops them. It also keeps out debris, leaves, and whatever else comes off your roof. Don’t skip the screen.

Step 5: Redirect the Downspout

Cut your existing downspout to feed into the barrel. Most neighborhood hardware stores sell flexible downspout extenders for a few dollars. You’re basically just rerouting where that water lands. A diverter kit works well if you want a cleaner install and don’t want to cut anything permanently.

How Much Water Can You Actually Capture?

Here’s the part I find genuinely exciting, which tells you something about me. A standard rule of thumb is that one inch of rainfall on 1,000 square feet of roof yields roughly 600 gallons of water. My shed roof is about 200 square feet. Even a half-inch rain event brings in around 60 gallons, which is more than a full barrel. A typical Pacific Northwest summer storm before the dry season locks in? That can fill my barrel twice over if I’d had the overflow running to a second one.

August around here can go three to four weeks with essentially no rain. If I water my vegetable beds every other day with a full watering can (about 2 gallons per pass), a single full barrel gets me roughly 27 watering sessions. That’s real money, especially if you’re on a metered water supply. I’ve written before about deep watering techniques that stretch every gallon further, and pairing that with a DIY rain barrel is where things actually start adding up.

A Few Things I’d Do Differently

I didn’t raise the barrel high enough the first season. Getting a watering can under a 3-inch clearance while crouching next to a hot shed in August is not a vibe. Go higher. Also, paint the barrel if it’s translucent or light-colored. Algae loves sunlight and standing water. A coat of exterior spray paint takes five minutes and saves you from a gross surprise in July. Which, now that I think about it, is exactly the kind of thing you only learn by not doing it.

The whole project took me about two hours on a Saturday morning, including the cure time where I just stood around feeling pleased with myself. It’s not complicated. It’s just a barrel with some holes in it. But those holes are doing a lot of work come August, and I’ll take every drop I can get for free.

Especially when my past self was paying for water that was already falling out of the sky. You hate to see it.

Photo by Chelaxy Designs on Unsplash