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Rainwater harvesting with IBC totes, done properly.
This is the most popular second life a retired container gets, and most of the systems we see could be twice as good for about forty dollars more. The difference is almost always the same three things: a first-flush diverter, a screened and light-proof tank, and a stand that will still be level in three years.
Short answer
Size for the storm, not the year: ~0.6 gal per sq ft of roof per inch of rain. Add a first-flush diverter, screen every opening, block light to stop algae, and drain below the outlet before a hard freeze.
- Yield
- 0.6 gal/sq ft/in
- Head pressure
- 0.43 psi per ft
- Stock
- Grade B / C
- Full tote
- ~2,435 lb
Form 01 · Spec request
Buying totes for a build?
Tell us the volume, whether the water touches food, and whether you want them delivered or collected. Grade B and C stock is the cheapest thing we sell and the right feedstock for this.
Sizing
Work out what you can actually catch.
| Roof area | 0.5" storm | 1" storm | 2" storm | Totes to catch a 1 in storm |
|---|---|---|---|---|
| 500 sq ft | 150 gal | 300 gal | 600 gal | 2 × 275 |
| 1,000 sq ft | 300 gal | 600 gal | 1,200 gal | 3 × 275 |
| 1,500 sq ft | 450 gal | 900 gal | 1,800 gal | 4 × 275 |
| 2,500 sq ft | 750 gal | 1,500 gal | 3,000 gal | 6 × 275 |
| 5,000 sq ft (barn) | 1,500 gal | 3,000 gal | 6,000 gal | 11 × 275 |
Build order
Six stages, in sequence.
- 01
Build the stand first
A full 275 gallon tote is about 2,435 pounds. Build a level, load-rated stand on compacted ground or a slab before anything else. Every foot of height gives 0.43 psi of head.
2,435 lb per tote - 02
Fit the first-flush diverter
Route the first few gallons off the roof to waste. It carries the dust, grit, pollen and droppings that would otherwise settle in your tank and feed everything living in it.
The best $30 you will spend - 03
Screen every opening
Fine mesh on the inlet and on the overflow. Unscreened openings are how mosquitoes get in and how leaf litter turns a tank into a compost bin.
Mesh, not luck - 04
Manifold the tanks
Link totes at the outlet with 2-inch buttress adapters and hose or pipe. Linked at the bottom they fill and draw as one vessel and equalise automatically.
Bottom-linked - 05
Pipe the overflow
Take the overflow away from the stand and away from your foundation. A tank that overflows onto its own footings will not be level next season.
Away from the base - 06
Block the light
Black UV-stabilised bottles, an opaque wrap, or permanent shade. This is what stops algae, and it also protects the polymer from long-term UV embrittlement.
No light, no algae
Parts list
What a two-tote system needs
- Two grade B or C 275 gallon totes
- Two 2" buttress-to-camlock or hose adapters for the manifold
- Linking hose or pipe with clamps
- 3/4" garden hose adapter on the draw-off
- First-flush diverter sized to the roof area
- Fine mesh screen for inlet and overflow
- Overflow pipe and fittings
- Level, load-rated stand or slab
- Opaque wrap or shade structure if the bottles are natural
We sell every fitting on that list individually — see accessories and parts.
Mistakes
What goes wrong, in order of frequency
- No first-flush diverter, so the tank silts up and grows things
- Translucent bottle in full sun, green within a month
- Unscreened overflow, which is a mosquito door
- A stand that was level on the day and is not now
- Left full through a freeze — permanent bottle set, bowed cage
- Using an undocumented industrial tote for edible-crop irrigation
- Expecting sprinkler pressure from gravity head
Pressure, and why your sprinkler will not work
Gravity gives you about 0.43 psi per foot of elevation measured from the water surface to the outlet. A tote on a four-foot stand therefore delivers roughly 1.7 psi when full and less as it empties. That is entirely adequate for drip irrigation, soaker hose and filling a watering can, and nowhere near enough for a sprinkler head, a pressure washer or a hose-end sprayer.
If you need real pressure, use a pump. Raising the tank is the wrong solution: getting to 20 psi by elevation alone would require a stand roughly forty-six feet tall holding a ton of water, which is a structure, not a stand.
Water quality and what you may use it for
Harvested rainwater from a roof is not potable and should not be treated as such without a proper treatment system. For irrigating ornamental plantings, washing equipment, flushing and topping up ponds it is excellent.
For irrigating edible crops, the container history matters as much as the water, because irrigation water contacts the produce. Use documented food-grade stock for that, and check local rules — some jurisdictions regulate rainwater harvesting, and a few restrict it.
Winterising
Drain to below the outlet before the first hard freeze. Water expands as it freezes, and a full bottle in a Cleveland January will take a permanent set and push the cage outward. If the system has to stay live through winter, insulate the tank, heat trace the manifold and keep water moving — or accept that you will be buying a replacement bottle in spring.
Questions
Rain harvesting, answered.
01How much rain will I actually collect?
Roughly 0.6 gallons per square foot of roof per inch of rainfall, after allowing for losses. A 1,000 square foot roof in a one-inch storm yields about 600 gallons — which fills two 275 gallon totes and overflows the second one. Size for the storm, not for the year.
02Which grade of tote should I use?
Grade B or C for irrigation of non-edible plantings, washdown and general storage. Documented food-grade stock if the water will touch edible crops or livestock, because irrigation water contacts what you eat.
03How do I stop algae?
Block the light. Algae needs sunlight, and a translucent natural bottle in full sun will green up within weeks. Use a black UV-stabilised bottle, wrap the cage in opaque material, or site the tank in permanent shade. Keeping the tank sealed except at screened inlets also helps.
04Do I need a first-flush diverter?
If your water touches anything you care about, yes. The first few gallons off a roof carry dust, bird droppings, pollen and grit. A diverter routes that away before the clean water reaches the tank, and it is the single highest-value addition to any system.
05What about freezing?
Water expands. A full tote left through a hard freeze will take a permanent set and bow the cage outward. Drain to below the outlet before winter, or insulate and heat trace if the system must stay live.
06How high should the stand be?
Every foot of elevation gives roughly 0.43 psi. A four-foot stand gives about 1.7 psi, which is enough for gravity drip irrigation but not for a sprinkler. If you need real pressure, use a pump rather than a taller stand.
Build reference
Sizing, parts and pressure, in tables.
| Roof area | 0.25 in | 0.5 in | 1 in | 2 in | Totes to catch 1 in |
|---|---|---|---|---|---|
| 250 sq ft | 38 | 75 | 150 | 300 | 1 |
| 500 sq ft | 75 | 150 | 300 | 600 | 2 |
| 750 sq ft | 113 | 225 | 450 | 900 | 2 |
| 1,000 sq ft | 150 | 300 | 600 | 1,200 | 3 |
| 1,500 sq ft | 225 | 450 | 900 | 1,800 | 4 |
| 2,500 sq ft | 375 | 750 | 1,500 | 3,000 | 6 |
| 5,000 sq ft | 750 | 1,500 | 3,000 | 6,000 | 11 |
| Stand height | Pressure, tank full | Pressure, tank a quarter full | Runs | Does not run |
|---|---|---|---|---|
| 1 ft | 0.43 psi | 0.11 psi | Gravity fill | Anything with a nozzle |
| 2 ft | 0.87 psi | 0.22 psi | Short soaker hose | Drip emitters reliably |
| 4 ft | 1.73 psi | 0.43 psi | Drip irrigation | Sprinklers |
| 6 ft | 2.60 psi | 0.65 psi | Longer drip runs | Sprinklers |
| 10 ft | 4.33 psi | 1.08 psi | Multiple zones | Pressure washers |
| Part | Quantity | Spec | Why |
|---|---|---|---|
| 275 gal totes, grade B or C | 2 | Black bottle if possible | Light control prevents algae |
| Buttress adapters | 2 | S60x6 to camlock or hose | Bottom manifold |
| Linking hose or pipe | 1 | With clamps | Bottom-link so tanks equalise |
| Garden hose adapter | 1 | 3/4 in GHT | Draw-off |
| First-flush diverter | 1 | Sized to the roof area | The highest-value addition |
| Mesh screen | 2 | Fine | Inlet and overflow |
| Overflow pipe and fittings | 1 set | At least inlet size | Route away from the stand |
| Stand or slab | 1 | Level, load-rated | A full tote is over a ton |
Next step
Two totes and forty dollars of fittings.
Tell us the roof area and whether the water touches food. We will spec the tank count and the parts list.