Guide · build walkthrough
Rainwater harvesting with IBC totes, done properly
A tote under a downspout will collect water. A tote with a diverter, a screen, a level base and a proper overflow will collect cleaner water without damaging your building. The extra parts are modest and worth it.
Get rain totes quoted for your roof
Roof area, number of downspouts, and whether the water touches edible crops. A partner supplier will follow up.
Yield by roof area and rainfall
| Roof area | 0.25 in rain | 1 in rain | 2 in rain |
|---|---|---|---|
| 400 sq ft | 53 gal | 212 gal | 424 gal |
| 800 sq ft | 106 gal | 424 gal | 847 gal |
| 1,200 sq ft | 159 gal | 635 gal | 1,271 gal |
| 1,500 sq ft | 199 gal | 794 gal | 1,589 gal |
| 2,000 sq ft | 265 gal | 1,059 gal | 2,118 gal |
| 5,000 sq ft | 661 gal | 2,646 gal | 5,293 gal |
Each square foot of roof sheds about 0.623 gallons per inch of rain; real capture is lower because of splash, evaporation and the first flush. Storage is usually the limiting factor. Rainwater collection rules vary by state and locality, so check local rules before building a large bank.
The build, step by step
- 01
Pick a tote with a history you trust
Benign prior content such as food products, water or soaps. For edible-crop irrigation ask for a documented food history or a rebottled unit. Never a pesticide or solvent bottle.
- 02
Build a level, solid base
A full 275 gallon tote weighs well over a ton (water alone is about 2,290 lb). Use compacted gravel, a concrete pad, solid blocks laid flat, or a rated steel stand. Never hollow blocks on their side, never bare soil.
- 03
Fit a first-flush diverter
The first runoff carries grit, droppings, pollen and shingle granules. Mount the diverter where you can service it, with the drain aimed away from the foundation.
- 04
Screen the inlet
Fine mesh under the lid, tensioned so it cannot sag into the water. It keeps leaves out and mosquitoes from breeding.
- 05
Plumb the overflow properly
An overflow pipe that discharges well away from the building. This fitting does the most to protect your structure.
- 06
Link additional totes bottom-to-bottom
A manifold between the outlets lets the bank fill and draw evenly. Route the overflow from the last tote.
- 07
Fit the outlet you will actually use
A hose adapter on the valve for general use, a tap at a convenient height for buckets, or a full-bore line for drip irrigation. Keep the bore large; necking down to a garden hose cuts the flow.
- 08
Block the light
A black bottle, UV jacket or plywood shroud. Algae needs light; remove it and the problem largely disappears.
- 09
Winterise before the first hard freeze
Drain down, leave the valve open, and bypass the diverter so the downspout runs straight through.
Sizing the bank to the use
| Use | Totes | Notes |
|---|---|---|
| Small vegetable garden | 1 | One tote covers short dry spells |
| Large home garden | 1–2 | A linked pair gives a buffer |
| Greenhouse | 2–3 | Demand is steady |
| Market garden | Several | Manifold and pump needed |
| Livestock (non-potable) | Several | Float valve and protection from animals |
| Construction dust suppression | 2–4 | Grade C is fine |
Size to your own demand and rainfall. These are starting points, not calculations.
Is harvested rainwater safe?
For soil irrigation of most crops it is widely used. Things to think about: roof material (avoid heavily degraded asphalt and treated timber shakes), the first flush (it is the dirty part), and the tote’s prior content.
It is not drinking water without treatment, and a used tote is not a drinking-water vessel. For potable or emergency drinking supply, use a new bottle with a potable-rated gasket and treat the water appropriately; check local health guidance.
Questions people actually ask
How much rain do I need to fill a 275 gallon tote?
About one inch of rain on roughly 520 square feet of roof, at 85% collection efficiency.
Why does my rain tote smell?
Usually organic matter that got past the screen, or growth encouraged by light. Screen the inlet, fit a first-flush diverter, block the light and clean the bottle once a season.
Can I pressurise a rain tote for a sprinkler?
Not by raising it; use a small pump. Gravity gives about 0.43 psi per foot of elevation, which suits drip and flood irrigation but not sprinklers.
Will the tote survive winter?
If you drain it down and leave the valve open, usually yes. A full tote in a hard freeze can split, typically near the outlet.
Parts list for a rain tote system
What a typical build needs. Pricing for totes and parts is by quote from partner suppliers.
- Rain-grade tote(s) with a benign or documented food history.
- First-flush diverter sized for your downspout.
- Inlet screen of fine mesh for each opening.
- Overflow fitting and pipe to carry surplus well away from the building.
- Linking manifold and isolation valves if you connect more than one tote.
- Tap or hose adapter for the outlet valve.
- Level base: compacted gravel, a slab or a rated stand.
- Filter if you feed drip irrigation.
- Pump (optional) if you need pressure.
- UV protection: a black bottle, jacket or shroud.
Winter, mosquitoes, and the two maintenance jobs a year
Autumn: the drain-down
Drain down, leave the valve open, open the lids slightly, and bypass the diverter so the downspout runs straight through. A full tote in a hard freeze can split, and the bottle is then finished, though the cage and base are usually fine and a replacement bottle may be an option.
Spring: the clean-out
Drain fully, scrub the inside with a long brush, rinse, and check the screens and the diverter. Sediment builds up even with a good diverter.
Mosquitoes, all season
Exclusion works best: fine mesh on every opening, a sealed overflow, and no standing water in the diverter between storms. Larvicides are a second line and may not be suitable if the water touches edible crops; follow the product label.
Algae, all season
Block the light and the problem largely goes away.
What actually breaks
Usually not the tote. The diverter clogs, the screen sags into the water, or the overflow erodes the ground. All three are quick checks.
More rainwater questions
Can I use rainwater in a greenhouse misting system?
Only with good filtration. Misting nozzles are finer than drip emitters and block easily, so expect to change filter cartridges.
How do I keep the water from smelling?
Screen the inlet, fit a diverter, block the light, and clean once a season. Smell comes from decomposing organic matter, and all four steps reduce how much gets in.
Is it worth insulating a rain tote?
In mild winters an insulating jacket can help keep the system in use. In colder climates, draining down is more reliable.
Can I bury a tote?
No. An IBC bottle is not designed for soil loading, and the cage does not help. Buried tanks are a different product.
Troubleshooting a rain system
| Symptom | Likely cause | Fix |
|---|---|---|
| Tank fills slowly in heavy rain | Diverter undersized or clogged | Clear it or fit a larger one |
| Water smells | Organic matter, biofilm | Screen the inlet, clean the tank |
| Green water | Light | Black bottle, jacket or shroud |
| Mosquito larvae | Unscreened opening | Fine mesh on every opening |
| Sediment in the bottom | No first-flush diverter | Fit one; clean the tank |
| Drip emitters blocking | No filtration | Add a filter before the line |
| Very low flow | Necked-down plumbing | Keep a large bore to the point of use |
| Tote tilting | Soft or uneven base | Rebuild the base properly |
| Overflow eroding ground | Uncontrolled discharge | Pipe it away, add a splash pad |
| Split bottle in spring | Left full over winter | Replace the bottle; drain down next autumn |
| Algae despite a black bottle | Light through the inlet or lid | Opaque lid and a shaded, screened inlet |
| Tank empties faster than expected | Leak at a fitting or manifold | Check every fitting under load |
More rainwater questions
How much does a rain tote system cost?
It depends on the number of totes, the parts and your base. Pricing for totes and parts is by quote from partner suppliers.
Can I collect from a metal roof?
Metal roofs generally give clean runoff. Be cautious with copper or zinc flashing if the water will go near fish.
Should the tank be raised?
Only enough for gravity draw, at about 0.43 psi per foot. A full tote is very heavy, so a tall stand adds risk for little pressure; a small pump is often the better choice.
Do I need to treat the water?
For soil irrigation, usually not. For anything touching edible parts of plants near harvest, filter it and consider the roof material. Drinking water needs a different system and proper treatment.
Where people go from here
Reuse first, then recycle.