Catch Rain With a Simple Barrel: Set It Up, Size It Right, and Use It Wisely

Rain that falls on your roof is free water that most of us just send down the drain. Catch it in a barrel and you have soft, chemical-free water for your garden, your trees, and your washing chores, and you stop a fair bit of storm runoff from carrying soil and fertilizer into the street. You do not need pumps, tanks, or permits for a basic home rain barrel. A barrel, a downspout diverter, and about an hour of work is enough to get started.

This guide covers how to set up a simple rain barrel, how to figure out how much water you can actually catch, and the important part most quick guides skip: what this water is safe to be used for, and what it is not.

What a Rain Barrel Actually Is

A rain barrel is just a covered container that sits under a downspout and catches the runoff from your roof. The water flows down the gutter, through a diverter or a short piece of flexible downspout, and into the barrel. A spigot near the bottom lets you fill a watering can or attach a short hose.

A basic setup has a few parts:

• a barrel with a lid and a screen or fine mesh over the opening
• a way to connect the downspout to the barrel, either a rigid downspout diverted into a hole in the lid or a flexible downspout extension
• an overflow fitting near the top so extra water has somewhere to go when the barrel fills
• a spigot near the bottom, above any sediment that settles
• something solid to set the barrel on so the spigot is easy to reach and the barrel does not sink into mud

You can buy a barrel ready to go, or build one from a food-grade container. Either way, cover the opening so leaves and mosquitoes cannot get in. Stagnant water in an open barrel is exactly where mosquitoes breed, so a tight-fitting lid with fine screening is not optional.

How Much Can You Catch

The rule of thumb is simple: for every inch of rain that falls on your roof, you can collect roughly 600 gallons per 1,000 square feet of roof. A smaller version of that math is easier to hold in your head.

• a 1,000 square foot section of roof catches about 600 gallons per inch of rain
• a 40 by 25 foot house with a simple pitched roof is around 1,000 square feet of footprint
• one decent storm, say half an inch of rain, would fill a standard 50 gallon barrel several times over

That number matters because it tells you two things. First, a single rain barrel fills very fast in a real storm, which is why the overflow opening is so important. You are almost never running out of rain, you are running out of storage. Second, if you want to make a real dent in your water use, a few barrels linked together hold more than one.

If you want a rough figure for your own place, measure the footprint of the roof that drains to the gutter you are using. Half of that number, multiplied by the rain in inches, gets you close to the gallons. You do not need to be exact for a home barrel, but it is worth knowing that one barrel is a small bucket compared to the rain your roof actually catches.

Using the Water Safely

Here is where the honest part comes in. Roof runoff is not drinking water, and it is not clean in the way tap water is clean. As it runs over the roof it picks up whatever has collected there: bird droppings, dust, pollen, bits of old shingle, and in some places pollution from the air. That matters, so let us be straight about what this water is good for.

Rain barrel water is well suited for:

• watering ornamental beds, lawns, shrubs, and trees
• watering container plants and houseplants
• washing garden tools, bikes, and outdoor gear
• cleaning windows and siding
• watering a compost pile to keep it cooking

Use more care with anything you are going to eat. Extension services disagree on exactly how cautious to be, and some do not recommend roof runoff on vegetable gardens at all, mostly because of animal droppings on the roof. If you do use it on food crops, the safer approach is to:

• water the soil at the base of the plant, not the leaves, so water does not splash onto the parts you eat
• stop using it a few weeks before harvest, and rinse produce thoroughly
• focus it on plants where the edible part is not touching the water, like fruit trees, rather than leafy greens you eat raw
• let the water go through a settling period and draw from the spigot, not the surface, to avoid the worst of the film

Do not use roof runoff for drinking, cooking, or bathing, and do not treat it as safe for pets to drink either. If you want rainwater for drinking, that is a completely different, much more careful system, not a barrel under a downspout. A simple home barrel is a watering and washing tool, and it is a good one when you use it that way.

Keeping It Clean and Winter-Ready

A rain barrel needs very little upkeep, but a few habits keep it pleasant and useful.

• check the screen regularly and clear off leaves so water keeps flowing in
• empty and rinse the barrel once a year, usually in the fall before you disconnect it
• if algae starts to grow on the inside in summer, keep the lid on tight and block light; that fixes most algae problems
• use the water as you collect it so it does not sit stagnant for weeks at a time

In cold climates, you need to shut the barrel down for winter. Ice will crack a plastic barrel and can ruin the spigot. Before the first hard freeze:

1. empty the barrel completely
2. disconnect it from the downspout and turn it upside down or store it indoors
3. put the downspout back on the gutter so snow and ice do not overflow the gutters

When spring comes, set the barrel back up, give it a quick rinse, and you are collecting again.

Good Enough to Start

You do not need a full rainwater system to get value out of this. A single barrel under one downspout will carry your flower beds through dry stretches, save you carrying the hose everywhere, and cut the runoff that would otherwise wash down the gutter into the street. Keep it simple, keep it covered, and use the water for what it is actually good for. That is neighborly self-reliance at its most practical, one barrel of free water at a time.

---

— C. Steward 🥕