Self-Reliance · Water · Project Guide
A 55-gallon rain barrel is the simplest water infrastructure a household can add. Here's the math, the setup, and what to buy, for $80 to $150.
Content based on official guidance from FEMA, the American Red Cross, and the CDC.
Start here
The math is straightforward. Most households are surprised by how much they're currently sending down the storm drain.
The formula
Roof area (sq ft) × Rainfall (in) × 0.623
That gives you gallons collected at roughly 90% efficiency, accounting for first-flush losses and splash.
Example
A 600 sq ft roof section, one inch of rain
600 × 1 × 0.623 = 374 gallons per rainfall event. A 55-gallon barrel fills completely after about 0.15 inches of rain on a 600 sq ft catchment. That's a light afternoon shower.
What the math means in practice
A single barrel fills fast
In most of the US, you'll fill a 55-gallon barrel multiple times per month during spring and early summer. The constraint is barrel capacity, not rainfall.
55 gallons waters a 4×8 raised bed twice
A standard raised bed needs about 2 gallons per square foot per week. One full barrel covers a 32 sq ft bed for roughly two weeks of hand-watering.
Two downspouts, two barrels
Most houses have two to four downspouts. Installing one barrel per downspout on the garden side of the house doubles capacity without doubling complexity.
Before you buy
Not every plastic barrel is safe for water you'll put on edible plants. One word on the label changes everything.
01
Material
Look for the recycling symbol with the number 2 stamped on the barrel. HDPE is food-safe and doesn't leach chemicals into the water. The barrel should be opaque, not clear, to block light and prevent algae growth.
02
Previous use
Repurposed barrels are common and usually fine — but only if their previous contents were food or beverage grade. Olive oil, juice, and soda syrup barrels are ideal. Barrels that held industrial chemicals, cleaning products, or pesticides are not safe to repurpose, regardless of how well you rinse them.
03
Features to confirm
A functioning spigot near the bottom, a closed lid (not just a loose cover), and a dedicated inlet port at the top are the three non-negotiables. Confirm all three before buying a bare barrel and retrofitting, as converting an unmodified drum adds cost and trouble.
The blue barrel rule of thumb
Blue is the unofficial color convention for food-grade water storage. If you see a blue 55-gallon barrel, it's almost certainly food-safe HDPE. White barrels are more common in industrial contexts and worth extra scrutiny. Color alone is not a guarantee, but it's a useful filter when evaluating used barrels.
The setup
No plumber needed. The only tool required is a hacksaw and a drill. Most installations take 90 minutes or less.
Pick the downspout closest to where you water. Set the barrel on two or three concrete blocks, or a purpose-made stand. Elevation is important: a barrel sitting 12 inches off the ground delivers usable water pressure through the spigot. A barrel on bare ground does not.
Hold the diverter against the downspout at the correct height and mark the cut line with tape. Most residential downspouts are 2×3 inches or 3×4 inches. Measure yours before ordering the diverter, not after. Cut the downspout with a hacksaw, keep the cut square.
The diverter slides into the cut and attaches with the included screws. It works passively: when the barrel is full, water bypasses the hose and continues down the downspout to the ground. Connect the included hose between the diverter's outlet and the barrel's inlet port.
Before the first rain, confirm there's a mesh screen at every open port. The inlet where the fill hose enters the barrel is the critical one. A 1/16-inch mesh or finer keeps mosquitoes out. Standing water with no screen is a breeding site within 7 to 10 days. Most quality barrels include a built-in screen, but check and do not assume.
Most common setup mistake
A rain barrel without a sealed inlet port will breed mosquitoes within one week of filling. It's the most frequently skipped step and the most consequential one. If your barrel's inlet screen is damaged or absent, replace it before the barrel goes in.
Tools needed → hacksaw, drill, tape measure
Stability note
A full 55-gallon barrel weighs about 460 pounds. Place it on a flat, stable surface before filling. Two standard concrete blocks laid flat and level on compacted ground is the most common approach. Purpose-made wooden or cinder-block stands work well. Never place the barrel directly on soil that freezes and heaves.
Often overlooked
Overflow is not a small detail. An uncontrolled overflow routes water directly against your foundation, which causes problems that are expensive to fix.
Most rain barrels include an overflow port near the top. If yours doesn't, drill a 1-inch hole about 2 inches below the rim and fit a barbed hose fitting with waterproof sealant.
Attach a length of garden hose to the overflow port and route it to a garden bed, a lawn area, or a drainage swale. The hose should slope continuously away from the barrel and from the house. A minimum 6 feet of distance from the foundation is the standard recommendation.
In most of the US, a 1-inch rainfall event produces far more than 55 gallons from a standard roof section. Your barrel will fill and overflow during any meaningful rainstorm, not just heavy ones.
The diverter handles some of this by redirecting excess water back down the downspout once the barrel is full. The overflow port handles the rest. Both need to work. Test the overflow path before the first rainstorm, not during it.
Chaining two barrels together
If you want 110 gallons of storage from a single downspout, connect two barrels in series. Route the first barrel's overflow port into the second barrel's inlet with a short length of hose. The second barrel's overflow port routes away from the house as normal. This doubles capacity with minimal added installation work.
End of season
Water expands when it freezes. A barrel that's ignored through the first hard freeze can crack along the seams. Five minutes of work in the fall prevents a $100 replacement in the spring.
In most of the northern US, late October to mid-November is the window. Don't wait for the forecast to show a freeze, because a 28-degree night with no warning is common in that range. Aim for mid-October as a rule.
Open the spigot and let it drain completely. Tilt the barrel if needed to get the last few gallons out. Even a few inches of standing water at the bottom is enough to crack the barrel if it freezes.
Remove the fill hose from the diverter and re-route the downspout section so water flows normally to the ground. Most diverters have a simple cap or bypass that handles this in seconds.
A garage or shed is ideal. If the barrel has to stay outside, turn it upside down so it can't collect water or debris. This also extends the life of the spigot hardware.
Mild climates
If you're in the southern US, California coast, or Pacific Northwest and hard freezes are rare, you can leave the barrel in service through winter. Running water through it during winter months actually helps keep debris from accumulating. Give it a rinse with a dilute bleach solution once a year regardless of climate.
Spring startup
In spring, rinse the barrel with a weak bleach solution (1 tablespoon per gallon of water), let it sit for 15 minutes, drain fully, and rinse clean. Reinstall on the blocks, reconnect the diverter fill hose, and you're ready for the season's first rain.
What to buy
Four items. Most households already have the blocks. The rest ships to your door in a day or two.
Standard window screen material, cut to size. Cheapest way to replace or reinforce a damaged inlet screen. Cut a piece 2 inches larger than the opening, secure under the lid or port cover. Replace annually or when you see tears.
Find at any hardware store
Two standard 8×8×16 concrete blocks laid flat create a stable base and lift the barrel about 7 inches — enough for a watering can to fit under the spigot. About $3 per block at any hardware store.
Find at local hardware store
Total project cost
$80 – $150
Less if the barrel comes with the diverter and screen included.
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Legal status
Almost certainly yes, but worth a quick check if you're in the western US.
The vast majority of US states have no law restricting residential rainwater collection and many actively encourage it with rebate programs. If you're east of the Rockies, you almost certainly have no legal issue to research.
Some states, Texas and Oklahoma among them, have laws that specifically protect the right to collect rainwater.
A handful of western states historically restricted rainwater collection under prior appropriation water law. Most have since updated their statutes. Colorado, for example, legalized collection in 2016 and permits up to 110 gallons per household.
If you're in Arizona, Nevada, or Utah, look up your state's current statute before installing. A 55-gallon barrel rarely triggers any restriction even where limits exist, but verify.
NCSL state-by-state rainwater lawsWhat's next
Water storage, filtration, and catchment are three distinct tiers of water independence. The water hub maps all of them out.