Let's Talk About Water

Last issue we told you what we're building. This one is about what goes in it.

If you're thinking about a rain barrel for the first time — or you've had one for years and never quite felt sure about using it on your tomatoes — this is for you. We pulled guidance from UMN Extension, Rutgers, and a stack of university research, then translated it into plain English. No scare tactics. No hand-waving. Just what we'd tell a neighbor over the fence.

Picking a Rain Barrel

The good news is it's hard to get this wrong. Most 55-gallon barrels do the job. But a few things actually matter:

• Food-grade material. Start with a barrel that originally held food (olives, juice, pickles). Avoid anything that held industrial chemicals. The Recycling Association of Minnesota sells subsidized food-grade barrels every spring — we recommend them.
• Opaque, not translucent. Light is what algae needs to grow, and a barrel that lets sunlight through will turn green inside within a few weeks of warm weather. Algae isn't dangerous on its own, but it clogs drip emitters, gunks up pump intakes, and makes the water less pleasant to work with. Dark, opaque plastic keeps the inside of the barrel dark and the water clean.
• A tight-fitting screen on top. Keeps leaves, sticks, mosquitoes, and curious squirrels out. Non-negotiable for health and for not attracting wildlife.
• An overflow outlet. When the barrel fills, you want the extra water directed somewhere useful — a garden bed, a tree, a rain garden — not your foundation.
• A spigot at the bottom. And raise the whole thing on cinder blocks or a sturdy platform so you can actually get a watering can under it.
• A removable lid — and ideally a pre-drilled port. If you're planning to run a Greenway Drip kit (or any pump-based system), you'll need to get inside the barrel to place the pump, and you'll have a tube and a thin wire running out the top. A fully removable lid makes installation painless. Better still: some barrels come with a pre-drilled port or knockout near the top, which saves you from drilling through plastic yourself.

One barrel captures a lot of rain. A half-inch of rainfall fills a 55-gallon barrel off a modest roof section. An inch of rain on 1,000 square feet of roof generates about 600 gallons. If you have the space, two barrels linked together are better than one.

A Word on Standalone Rain Catchers

Everything above assumes you're hooking a barrel to a downspout. But there's another option: standalone rain catchers that collect rain directly from the sky instead of routing it off your roof. A wide catchment surface — a funnel, a tarp on a frame, or a purpose-built basin — feeds straight into a storage tank. No roof involved.

Where it shines. A lot of the best growing spaces don't have a roof attached to them. Community garden plots. Allotments. The raised beds tucked along the Greenway. Schoolyards. Church lawns. A friend's sunny backyard corner nowhere near the house. Standalone catchers make rainwater irrigation possible in all of those places — a big deal if your only alternative used to be hauling water from a spigot.

There's a safety angle too: most of the contamination concerns in the next section come from the roof, not the rain itself. Rain falling directly into a clean catchment skips the dirtiest part of the equation entirely.

The tradeoff is catchment area. A roof is huge, and that's why rooftop systems fill so fast. A standalone catcher collects only as much rain as its opening can catch. For a small herb bed, that can be plenty. For a full vegetable garden, it's usually a supplement — though in a community plot, "supplement" might be exactly what you need.

The Honest Conversation About Safety

Here's where it gets real. The question we hear most: is it safe to use on my vegetable garden?

The short answer from University of Minnesota Extension: rain barrel water is not potable, and they recommend it not touch the edible parts of plants you'll eat — greens, berries, root crops, herbs. Municipal water is tested for pathogens. Rain barrel water is not.

Two things are actually worth worrying about:

1. Pathogens from the roof. Bird droppings, squirrel visits, pollen, the occasional dead bug. When rain washes the roof, it washes all of that into your barrel. Studies have found bacteria like E. coli in rain barrel water often enough to take seriously.

2. Roofing materials. Asphalt shingles can leach small amounts of hydrocarbons. Older roofs (pre-1980s) may have traces of lead. Metal and clay tile roofs are the cleanest harvesting surfaces.

But here's the nuance worth knowing: the roof is where the concentration happens. Contaminants build up between rainstorms — bird droppings drying in the sun, shingle grit, pollen, dust — and then a single rain washes that accumulated load into your barrel all at once. Your garden soil, by contrast, gets rain directly and dilutes it, absorbs it, and breaks a lot of it down biologically. That's why roof-harvested water deserves more care than rain falling straight onto a bed. The good news: "more care" is mostly just a handful of simple practices.

How To Use It Safely

If you want to use rain barrel water on an edible garden — and we think, with care, you absolutely can — here's the stack of practices the research supports:

• Water the soil, not the plant. This is the single biggest one. Drip irrigation at the root zone bypasses the entire problem. No splash on leaves, no contact with fruit, no contamination of the edible parts. (Yes, we built our whole product around this.)
• Add a first-flush diverter. A simple device that redirects the first few gallons of each rainfall — the dirtiest part — away from your barrel. Cheap. Effective. Worth it.
• Treat monthly with bleach — or hydrogen peroxide if you prefer. Rutgers recommends one ounce of unscented household chlorine bleach per 55-gallon barrel, once a month. Wait 24 hours before using. If bleach isn't your thing, 3% household hydrogen peroxide is a reasonable substitute — University of Illinois Extension endorses it as an alternative. It breaks down into water and oxygen, with no chlorinated residue. The tradeoffs: it costs more and degrades faster, so it doesn't leave the same multi-day residual protection.
• Water in the morning. UV from sunlight has a real disinfecting effect on anything that does end up on plant surfaces. Early watering also lets leaves dry before you harvest.
• Wash your produce. Always, regardless of water source. A thorough rinse under potable water removes most surface contamination from any origin.
• Skip the leafy greens if you're worried. Lettuce, spinach, and low-growing herbs are the highest risk because the edible part is the part most likely to catch splash. Save the rain barrel for trellised tomatoes, fruit trees, peppers, and ornamentals.

What About Testing?

You can test rain barrel water, and some gardeners do. Your county extension office or local health department can point you to a lab, and a basic E. coli test runs about $25–40 in Minnesota.

The honest reality: testing gives you a snapshot of one moment. The next rainstorm resets it. UMN Extension's position is that testing would need to happen so frequently it's not practical for home use. If you're growing food commercially, that's a different conversation and you should talk to your state department of agriculture (for us in Minnesota, that's MDA). For a home garden, the practices above do more than any single test.

Winterizing (Because This Is Minnesota)

Come late October, drain your barrel completely, remove the hose and screen, give the inside a scrub with mild detergent, and store it upside down or covered. Water left in a barrel will freeze, expand, and crack it. Ask anyone who's learned this the hard way.

From Our End of the Hose

We picked a supplier. Samples arrived, we put them through their paces, and we've chosen the unit going into our first production run. The thing we were testing for was plug-and-play — open the box, connect four things, start watering. No wire splicing, no adapters, no trip to the hardware store halfway through setup. That was a hard line for us, and we finally found a partner who could meet it.

A note on where things come from. We want to be straight with you, because we think it matters. Our goal is to source every component of this kit locally — ideally from the Upper Midwest, ideally from people we can shake hands with. For this first year, we couldn't get there on every part. The solar panel and drip irrigation components are coming from domestic suppliers (better BPA-free verification, better tariff math, and we like the companies). The combined controller-battery-timer enclosure and the pump are coming from China, because no domestic equivalent currently exists for the pre-wired weatherproof unit we need. And because it's been a good excuse for Jasper to practice his Mandarin — K–8 immersion is finally paying off.

We're not thrilled about the distance, and we're already talking to local contract manufacturers here in Northeast Minneapolis about what it would take to bring assembly — and eventually more of the components — home. That's a multi-year project. We'll tell you honestly how it's going.

The demo beds are going in. Two raised beds in the front yard, running on the same kit we're selling. The mains: tomatoes, cucumbers on a trellis, zucchini, summer squash, sugar snap peas, green beans, eggplant, and peppers. The supporting cast: a generous herb section, plus sunflowers and nasturtiums for the pollinators (and because nasturtiums are edible, pretty, and refuse to be fussy). If you're in the neighborhood this summer, come by and poke around.

And one date for your calendar: we'll be at Art-A-Whirl (May 15–17) with a live system you can see running. Come find us.

If you made it this far — thank you. Reply and tell us: do you already have a rain barrel? What's worked? What's frustrated you? What do you want us to cover next?