How to Collect Water From Rain

There's something almost ridiculous about paying a water bill when thousands of gallons of perfectly good water fall on your roof every year. It's right there. Free. Renewable. And yet most of us just let it run down the driveway and disappear into the storm drains.

Rainwater collection isn't some fringe survivalist thing anymore. People are doing it in suburbs, on farms, and everywhere in between. Some folks use it to water their gardens. Others drink it. And a growing number of off-gridders rely on it as their primary water source.

Here's the good news: collecting rainwater is way easier than you think. You don't need fancy equipment or a degree in hydrology. You just need a roof, some barrels, and a little bit of know-how.

Let's break it down.

Why Bother Collecting Rainwater?

Before we get into the how, let's talk about the why — because if you're going to put in the effort, you should know what you're getting out of it.

It's Free Water

Seriously. Water bills add up. If you're watering a garden, washing cars, or running a homestead, those gallons get expensive fast. Rain doesn't cost anything.

You're Not Dependent on the City

Droughts happen. Water restrictions happen. Pipes break. If you've got a few hundred gallons of rainwater stored, you've got backup. That peace of mind is worth something.

It's Actually Better for Some Uses

Rainwater is naturally soft — no chlorine, no fluoride, no hard minerals clogging up your pipes. Plants love it. Your hair will too, if you're washing with it.

It's Sustainable

You're using what's already there instead of pulling from aquifers or rivers. If you care about that sort of thing (and honestly, more of us probably should), it's a solid move.

How Much Water Can You Actually Collect?

Let's do some quick math. Don't worry, it's easy.

For every inch of rain that falls on 1,000 square feet of roof, you can collect about 600 gallons of water.

So if you've got a modest house with a 1,500 square foot roof and you get 30 inches of rain per year, that's:

1.5 (roof size) × 30 (inches of rain) × 600 = 27,000 gallons per year

That's a lot of water. Even if you only capture half of it, you're still looking at over 13,000 gallons. For free. Just sitting on your roof, waiting.

The Basic Setup: What You Actually Need

Here's the thing about rainwater collection: you can make it as simple or as complicated as you want. Let's start simple.

The Bare Minimum System

The most basic setup looks like this:

That's it. You can set this up in an afternoon for a couple hundred bucks.

What Kind of Roof Works Best?

Not all roofs are created equal for water collection.

Good options:

Avoid:

If you've got a standard asphalt shingle roof, you're good to go. It's not perfect, but it's fine for gardens and non-drinking uses. If you're planning to drink the water, we'll talk filtration in a bit.

Gutters and Downspouts

You probably already have these. If not, you'll need to install them. Aluminum or vinyl gutters work fine. The goal is just to channel water from your roof to one collection point.

One tip: add gutter guards if you can. They keep out leaves and big debris so you're not constantly cleaning out sludge. You can get cheap ones at any hardware store.

Storage: Barrels vs. Tanks

This is where you have options.

Rain Barrels (50-100 gallons)

These are the entry-level choice. Cheap, easy to find, and you can daisy-chain multiple barrels together. They're great for watering gardens or washing outdoor stuff.

You can buy them new for $50-150, or sometimes get food-grade barrels for way cheaper from restaurants or factories. Just make sure they didn't store anything toxic.

Pros: Affordable, easy to set up, portable

Cons: Limited capacity, can freeze in winter, not suitable for heavy use

Large Tanks (200-10,000+ gallons)

If you're serious about rainwater — like using it as your primary water source — you need bigger storage. These can be plastic cisterns, stainless steel tanks, or even buried concrete tanks.

Pros: Massive storage capacity, can support full household use

Cons: Expensive, require more space, installation can be complex

How much storage do you need?

It depends on your goals:

The rule of thumb: store enough to get you through your dry season. If you don't get rain for two months, how much water will you need?

Setting Up Your First System

Let's walk through a basic rain barrel setup. This is perfect for beginners and costs under $200.

What You'll Need:

Step-by-Step:

1. Pick Your Spot

Find a downspout near where you need water. Ideally, pick one that drains a large section of roof. Make sure the ground is level and stable.

2. Elevate Your Barrel

Put your barrel on cinder blocks or a platform — at least 12-18 inches off the ground. This gives you gravity pressure so water actually flows out the spigot. Plus, you can fit a watering can underneath.

3. Install the Downspout Diverter

Cut your downspout and install the diverter according to the kit instructions. These are designed to send water into your barrel until it's full, then automatically divert overflow back to the downspout.

No diverter? You can just position the barrel under the downspout, but you'll need an overflow solution.

4. Add a Screen

Put mesh or screen over the top opening. This keeps out leaves, bugs, and especially mosquitoes (who will absolutely lay eggs in standing water if you let them).

5. Add a Spigot

If your barrel doesn't have one, drill a hole near the bottom and install a spigot. Make sure it's sealed tight with rubber washers and plumber's tape.

6. Set Up Overflow

Attach a hose to the overflow port (usually near the top of the barrel) and direct it away from your foundation. When the barrel fills up, the excess needs somewhere to go.

That's it. Wait for rain and watch it fill up.

Filtering and Purifying: Can You Drink This Stuff?

Straight rainwater collected in a barrel? Not for drinking. Not yet.

But with the right filtration, absolutely. People live off rainwater full-time. You just need to understand what you're dealing with.

What's Actually in Rainwater?

Rainwater itself is pretty clean — it's just evaporated water. But by the time it hits your roof, runs through gutters, and sits in a tank, it's picked up:

None of this is the end of the world. It just means you need filtration before drinking.

Basic Filtration

For non-drinking uses (garden, livestock, washing), you just need basic filtration to remove chunks and sediment:

These are cheap and easy. Install them between your downspout and tank.

Drinking Water Filtration

If you want to drink your rainwater, you need a multi-stage approach:

Stage 1: Sediment Filter

Removes particles, dirt, and debris. Usually 5-10 micron filters.

Stage 2: Carbon Filter

Removes chemicals, improves taste, and absorbs some contaminants.

Stage 3: UV Sterilization or Chemical Treatment

Kills bacteria, viruses, and other microorganisms.

Alternatives: Boiling works too (one minute at a rolling boil). Or water purification tablets in a pinch.

Lots of off-gridders use a Berkey filter or similar gravity-fed filtration system. They're pricey but they work really well and don't need electricity.

Testing Your Water

If you're drinking rainwater regularly, test it. You can get home test kits online or send samples to a lab. Test for:

Peace of mind is worth the $50-100 for a test.

Maintenance: Keep It Clean

Rainwater systems are low-maintenance, but not no-maintenance. Here's what you need to do:

Every Few Weeks:

Every Few Months:

Once or Twice a Year:

In Winter:

If you're in a freeze zone, you need to either:

Frozen barrels expand and crack. It's a mess. Don't skip this.

Legal Stuff: Is This Even Allowed?

Here's where it gets weird. In most places, yes, rainwater collection is totally legal. But there are exceptions.

United States:

Most states allow and even encourage rainwater harvesting. But a few (like Colorado, historically) have had restrictions based on old water rights laws. Those restrictions have loosened in recent years, but it's worth checking your state and local regulations.

Some places offer tax incentives or rebates for rainwater systems. Look into it — you might get money back.

Other Countries:

Australia and New Zealand actively encourage it. Canada's fine with it. Most of Europe allows it.

The bottom line: check your local laws before investing heavily, but chances are you're in the clear.

Common Mistakes (and How to Avoid Them)

Mistake #1: No First Flush Diverter

The first bit of rain washes all the crud off your roof. If you don't divert it, all that gunk goes into your tank. Invest in a first flush diverter or at least manually divert the first few minutes of rain.

Mistake #2: Forgetting About Mosquitoes

Standing water = mosquito paradise. Screen everything. Check regularly. No excuses.

Mistake #3: Not Planning for Overflow

Your barrel will fill up eventually. If you don't plan for overflow, water pools around your foundation. That's how you get basement flooding and foundation damage.

Mistake #4: Undersizing Your Storage

People always wish they'd gotten bigger tanks. Start with what you can afford, but plan to expand.

Mistake #5: Using the Wrong Barrel

Don't use barrels that stored chemicals or oil. Only use food-grade containers. Seriously.

Taking It to the Next Level

Once you've got the basics down, here are some upgrades:

Automatic Pumps

Add a 12V or electric pump so you can actually pressurize your water system. This lets you run hoses, sprinklers, or even indoor plumbing.

Rainwater for Indoor Use

With proper filtration, you can plumb rainwater into your home for toilets, laundry, and showers. Drinking water needs the most filtration, but non-potable uses are easy.

Multiple Tanks in Series

Connect tanks with overflow pipes so when one fills, it automatically fills the next. This is how you scale up to thousands of gallons.

Buried Cisterns

In areas where freezing is an issue, or if you want to save space, bury your tanks. They stay cooler in summer and won't freeze in winter (below the frost line).

Drip Irrigation Integration

Hook your rain barrels directly to a drip irrigation system for your garden. Set it and forget it.

Real Talk: Is It Worth It?

Look, if you're just trying to save a few bucks on your water bill in the suburbs, a rain barrel might not be life-changing. You'll save maybe $20-50 a year on garden watering. Cool, but not exactly groundbreaking.

But if you're:

Then yeah, rainwater collection is absolutely worth it. It's one of those things that seems small until you need it, and then you're really glad you set it up.

Plus, there's something satisfying about using water that fell from the sky instead of getting a bill from the city. It's a small step toward independence, and sometimes that matters.

Getting Started This Weekend

You don't need to build the perfect system right away. Start small:

If you like it, add more barrels. If you love it, upgrade to larger tanks. If you're hooked, go full off-grid with filtration and pumps.

The point is to start. That water's falling on your roof right now, whether you catch it or not.

FAQ: Rainwater Collection

Is rainwater safe to drink?

Not straight from the barrel, no. But with proper filtration (sediment filter, carbon filter, and UV sterilization or boiling), it's absolutely safe. Millions of people worldwide drink rainwater as their primary source. Just filter it right and test it occasionally.

How long can you store rainwater?

Indefinitely, if stored properly. Keep it in sealed, opaque containers to prevent algae growth. Add a small amount of bleach (1/8 teaspoon per gallon) if you're storing for long periods without use. In practice, rainwater stored in clean, covered tanks stays good for months or years.

Do rain barrels attract mosquitoes?

Only if you let them. Seal all openings with fine mesh screen. Check regularly for any gaps. If mosquitoes can't get in to lay eggs, you won't have a problem. It's that simple.

Can I use rainwater for my washing machine?

Yes, and your clothes will thank you. Rainwater is naturally soft, which means you'll use less detergent and your fabrics will last longer. Just make sure you filter out sediment first so you're not pumping dirt into your machine.

What happens in winter?

In freezing climates, you either drain your system and disconnect it for winter, or you insulate/heat your tanks. Frozen water expands and will crack barrels and pipes. Many people just use their system spring through fall and disconnect for winter. If you're off-grid year-round, you'll need buried cisterns or insulated, heated tanks.

How much does a rainwater system cost?

Basic rain barrel setup: $100-300. Mid-range system with multiple barrels and better filtration: $500-1,500. Professional off-grid system with large tanks, pumps, and full filtration: $3,000-10,000+. Most people start small and expand over time.

Do I need a permit?

Usually not for basic rain barrels, but check your local building codes. Larger systems (especially if plumbed into your house) may require permits. Some municipalities actually offer rebates for rainwater systems, so it's worth checking with your city or county.

What if I don't have gutters?

You can still collect rainwater, but it's harder. You could install gutters just for water collection, or set up tarps/collection surfaces that drain into tanks. Gutters just make it way easier and more efficient.