Rainwater harvesting with IBC totes
A 275-gallon tote under a downspout is the highest-leverage thing you can do with a used container. It is also the build most people get wrong in four specific places.
- Sheet
- 45
- Revision
- 2026-10
- Scale
- 1:1
- Drawn at
- Peoria IL
Roof area times rainfall is the only sizing math that matters: 1,000 square feet of roof yields about 623 gallons per inch of rain, minus roughly 15% for splash and evaporation.
Sizing, properly
| Roof area | Yield per 1 in rain | Totes to catch it | Practical setup |
|---|---|---|---|
| 400 sq ft (shed) | ≈ 210 gal | 1 | Single 275 on blocks |
| 1,000 sq ft (garage) | ≈ 530 gal | 2 | Two totes manifolded low |
| 1,800 sq ft (house) | ≈ 950 gal | 3–4 | Bank with common header |
| 3,000 sq ft (barn) | ≈ 1,580 gal | 6 | Two banks of three, valved |
| 10,000 sq ft (shop) | ≈ 5,280 gal | 19+ | Staged banks with pumped transfer |
The four mistakes
No first-flush diverter
The first gallons off a roof carry grit, bird droppings and shingle granules. A simple standpipe diverter keeps that out of the tote and stops the sump from silting up.
Translucent bottle in sunlight
Light plus nutrients equals algae within three weeks. Paint it, wrap it, or build a shade panel. A natural HDPE tote left bare in the sun is a green soup factory.
Undersized overflow
Your overflow must be able to pass the full downspout flow or the tote becomes a fountain in the first real storm. Plumb it at least as large as the inlet and point it away from the foundation.
No freeze plan
In central Illinois, a full tote freezes solid and bulges. Drain below the valve line before the first hard freeze, or heat-trace and insulate if you need winter capacity.
Parts list for a solid single-tote build
- Grade B used 275-gal tote, water-safe last contents, triple rinsed.
- S60x6 to 3/4" garden hose adapter on the outlet valve, plus a brass ball valve.
- Downspout adapter and first-flush diverter with a cleanout cap.
- Bulkhead overflow fitting, 2" minimum, with insect screen.
- Vented top fitting with fine mesh — mosquitoes need 1.5 mm to get in.
- Four solid concrete blocks or a welded stand: 275 gallons weighs 2,290 lb when full.
- Opaque wrap, exterior paint or a shade structure.
“Elevate it before you fill it. Nobody has ever successfully lifted a full tote to fix the thing they forgot to put underneath.”
— Every fabricator, everywhere
Manifolding two or more totes
Totes connected low on the outlet side equalise and behave as one tank. Connect them high and you will spend your weekend wondering why the second tote never fills. Use full-bore fittings, put an isolation valve on each tote, and keep the header level — a quarter-inch slope across three totes is enough to make the low one do all the work.
- Common header at valve height, isolation valve per tote.
- One sacrificial tote first in line to catch the dirtiest inflow.
- Single overflow at the end of the bank, sized for full flow.
- A pump only if you need pressure — gravity is free and never fails.
What a good single-tote build costs to assemble
| Part | Spec | Cost | Skip it? |
|---|---|---|---|
| Grade B 275 gal container | Water-safe documented history | $38–52 | No |
| Opaque wrap or exterior paint | UV blocking | $0–40 | No — algae in 3 weeks otherwise |
| Downspout adapter | To your gutter size | $12–22 | No |
| First-flush diverter with cleanout | Standpipe type | $28–60 | No — this is the one people skip |
| Screened and vented inlet | 1.5 mm mesh maximum | $10–18 | No — mosquitoes |
| 2 in bulkhead overflow | Sized to inlet, screened | $14–26 | No |
| Brass ball valve | Replaces the butterfly | $24–34 | Optional but worth it |
| S60x6 to 3/4 in hose adapter | Garden hose thread | $9–18 | No |
| Concrete blocks or welded stand | 24 in for gravity head | $16–140 | No — decide before filling |
| Winter drain kit | One-pull drain below the sump | $18–30 | Not in Illinois |
- Filled weight
- 2,290 lb — concrete or a welded stand, never soil
- Gravity head for a hose
- 24 in minimum to be useful
- Collection efficiency
- About 85% of theoretical roof yield
- Algae onset, unshaded natural bottle
- About 3 weeks in summer
- Mosquito mesh
- 1.5 mm or finer, on every opening
- Freeze line
- Drain below the sump before the first hard freeze
Frequently Asked Questions
How many IBC totes do I need for my roof?
It depends on roof area. The sizing table shows about 1 tote for a 400 sq ft shed, 2 for a 1,000 sq ft garage, 3 to 4 for a 1,800 sq ft house and 6 for a 3,000 sq ft barn, assuming 85 percent collection efficiency.
Why does the water in my tote turn green?
Light plus nutrients produces algae, and the guide says an unshaded natural bottle can go green in about three weeks in summer. Paint the tote, wrap it in an opaque cover, or build a shade panel to block the light.
Do I need a first-flush diverter?
The guide lists skipping it as one of the four common mistakes. The first gallons off a roof carry grit, bird droppings and shingle granules. A standpipe diverter with a cleanout cap keeps that out of the tote and stops the sump silting up.
How strong does the stand need to be?
A full 275-gallon tote weighs about 2,290 lb, so use solid concrete blocks or a welded stand, never soil. Raising it about 24 inches also gives enough gravity head to be useful with a hose.
What do I do with a rainwater tote in an Illinois winter?
A full tote can freeze solid and bulge. The guide says to drain below the valve line before the first hard freeze, or insulate and heat-trace it if you need winter capacity. A one-pull winter drain kit is also described.
Next in the loop
Published 2026-03-04. 11 min read. Written by the crew that does the work, not a content agency.