We have built roughly 3,400 rain harvesting kits in bay F since 2021, which means we have also fielded roughly 3,400 follow-up questions. This is all of it: sizing, siting, first flush, overflow, mosquitoes, winter, and the two mistakes nearly everybody makes.
Why a tote is a good rain barrel and a bad water tank
A 275 gallon IBC holds five times what a typical rain barrel holds, costs less per gallon than almost anything else available, arrives on a forkliftable pallet, and comes in a steel cage that doubles as a mounting frame for a tap, a trellis or a pump. For garden-scale rainwater capture it is close to ideal.
It is a poor choice for long-term potable storage, for anything that needs to be buried, for pressurised systems, and for installations where appearance is the primary consideration. HDPE under UV gets brittle in a couple of years unless it is a black bottle or it is shaded — which is the single most common failure we hear about.
Sizing: the arithmetic is simple and surprising
Roughly 0.6 gallons of water lands on each square foot of roof per inch of rain, after losses. So:
| Roof area | 0.25 in rain | 0.5 in rain | 1 in rain | 2 in rain |
|---|---|---|---|---|
| 200 sq ft (shed) | 30 gal | 60 gal | 120 gal | 240 gal |
| 500 sq ft (garage) | 75 gal | 150 gal | 300 gal | 600 gal |
| 1,000 sq ft (half a house) | 150 gal | 300 gal | 600 gal | 1,200 gal |
| 1,800 sq ft (whole house) | 270 gal | 540 gal | 1,080 gal | 2,160 gal |
The surprise for most people is how quickly a single tote fills. A thousand square feet of roof fills a 275 gallon tote in about half an inch of rain. That is a single ordinary afternoon in Indiana. Which means your overflow design matters far more than your storage volume — a point we will come back to, because it is mistake number one.
Siting: four rules
- Level, load-bearing base. A full 275 gallon tote weighs about 2,400 pounds. That is a small car sitting on 48 by 40 inches. Compacted gravel or a concrete pad. Not timber decking, not soft ground, not blocks on turf.
- Elevated if you want pressure. Every foot of elevation gives you about 0.43 psi. A tote on a four-foot stand gives you around 1.7 psi at the tap — enough for a gentle gravity hose, nowhere near enough for a sprinkler. If you want real pressure you want a pump.
- Shaded, or use a black bottle. UV embrittles natural HDPE in one to two years. Shade, a cover or a black UV-stable bottle takes that past five.
- Overflow routed away from the foundation. See below, twice, because it is the mistake that causes actual damage.
First flush: the cheap component everyone skips
The first few gallons off a roof carry the bird droppings, grit, pollen and roof granules that accumulated since the last rain. A first-flush diverter is a vertical pipe section that fills before water reaches the tote, captures that initial volume, and drips it out slowly afterwards.
It costs very little, takes twenty minutes, and it is the difference between a tote full of water and a tote with two inches of sludge in the bottom after a season. Size it at roughly one gallon per 100 square feet of roof.
Mistake one: no overflow, or an overflow that is too small
Your tote will fill. Then it will keep receiving the entire output of your downpipe, and that water has to go somewhere. If the only path is the inlet screen, it backs up the downpipe and finds the nearest joint — frequently next to your foundation.
The overflow must be at least the same diameter as the inlet, positioned near the top of the bottle, and routed to somewhere you actively want water to go: a swale, a rain garden, a drain, or the next tote in a linked battery. Not a splash block two feet from the wall.
Mistake two: an open inlet, and then mosquitoes
Standing water plus an opening equals mosquito larvae within a week in summer. Screen the inlet with fine mesh, screen the overflow, and seal the six-inch lid around the inlet pipe. The standard rain kit we build ships with a leaf-screen inlet precisely because we got tired of explaining this.
If larvae do appear, mosquito dunks containing Bacillus thuringiensis israelensis are effective, cheap and harmless to plants and pets. Do not use household chemicals in a tote you will later water vegetables with.
Linking totes into a battery
Two to four totes manifolded together at the base with bulkhead unions behave as one large tank with one draw point, while remaining individually movable and able to fit through a doorway. 550 to 1,100 gallons without a single component you cannot carry with two people and a hand truck.
Connect at the base, not the top — base connections equalise the levels automatically. Use full-bore unions rather than garden hose fittings, because the flow rate between totes during a heavy rain is higher than people expect.
Winterising, specifically for the Midwest
A full tote that freezes solid will split. HDPE also gets brittle below about -20 °F, so handling damage goes up at the same time. Before the first hard freeze:
- Drain to below half, or drain completely if you will not use it.
- Open the valve and leave it open, so ice has somewhere to expand into.
- Disconnect and drain any linking manifold — that is where splits usually happen.
- Divert the downpipe back to its normal path for the winter.
Which grade to buy
Grade C. Without hesitation. A rain kit is non-potable water service, which is exactly what Grade C exists for — structurally sound, cosmetically tired, priced accordingly. Paying for a Grade A food-history unit to catch roof water is money set on fire.
The one exception: if you intend to water edible crops and you want to be careful about prior cargo, ask us for a documented food-history Grade C unit. We hold some back for exactly this, and we will confirm the provenance in writing.
Our standard kit — Grade C tote, steel stand, leaf-screen inlet, overflow port, bulkhead tap and a garden hose adapter — is on the upcycled builds page.
