212 rainwater builds later
The rain harvester is the fab bay's best-selling product and the one customers modify most after delivery. Here is what 212 of them taught us about what people actually need.
- Sheet
- 80
- Revision
- 2026-10
- Scale
- 1:1
- Drawn at
- Peoria IL
A 275-gallon container under a downspout is the highest-leverage thing anybody can do with a used tote. It is also the build where the difference between a good one and a bad one is four decisions that cost almost nothing.
We have now built 212 of these, from single units for garden sheds to eight-container banks on barn roofs. The sizing arithmetic is the easy part: 1,000 square feet of roof yields about 623 gallons per inch of rain, and about 85 percent of that actually reaches the tank.
| Roof | Yield per inch | Containers | Typical setup |
|---|---|---|---|
| 400 sq ft shed | ≈ 210 gal | 1 | Single 275 on blocks |
| 1,000 sq ft garage | ≈ 530 gal | 2 | Manifolded low, one overflow |
| 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, pumped transfer |
The four decisions
First-flush diversion
The first gallons off any roof carry grit, droppings and shingle granules. A standpipe diverter with a cleanout keeps that out of the sump. Skipped on 80% of DIY builds and it is why their sumps silt up.
Light exclusion
Natural HDPE plus sunlight plus nutrients equals algae in about three weeks. Paint it, wrap it or shade it. This is the single most common reason a harvester gets abandoned.
Overflow sized to inflow
The overflow must pass the full downspout flow or the container becomes a fountain in the first real storm. At least as large as the inlet, screened, aimed away from the foundation.
A freeze plan
In central Illinois a full container freezes and bulges. Either drain below the sump before the first hard freeze or heat-trace and insulate. There is no third option that ends well.
What customers added afterwards
We track post-delivery modification requests because they tell us what the standard build is missing. Across 212 units:
| Added later | Share of customers | Now offered as standard? |
|---|---|---|
| Welded stand for gravity head | 41% | Yes — 24 in stand option |
| 12V pump kit | 28% | Yes |
| Winter drain kit | 24% | Yes, and recommended by default in Illinois |
| Second container and manifold | 19% | Yes, manifold kit |
| Shade frame instead of paint | 11% | Yes — keeps the level visible |
| Finer inlet screening | 9% | Yes — mosquitoes need 1.5 mm |
The stand is the one that matters most and is hardest to retrofit. Nobody has ever successfully lifted a full container to put something underneath it — 275 gallons of water weighs 2,290 pounds. Decide the height before the first fill or live with it.
What we will not promise
- Not potable. These are built on Grade B containers with a documented water-safe history, and they are for irrigation, livestock, wash-down and shop use.
- Not a pressure system. If you need pressure, the pump kit is the answer and it has its own failure modes.
- Not maintenance-free. The diverter needs emptying and the screen needs clearing, and a harvester nobody services becomes a mosquito nursery.
- Not a substitute for checking local rules. A small number of jurisdictions still regulate harvesting, and that is your call to make.
Building your own?
The full build guide has the parts list, the diverter detail and the manifolding geometry. We would rather you built it right than bought it from us.