Rain harvesting is one of the best uses for IBC tanks, and the Midwest is an ideal region for it. Omaha receives approximately 31 inches of rainfall per year -- not as much as the Southeast, but more than enough to fill multiple IBC tanks during the growing season. A single 1-inch rainstorm on a 1,500-square-foot roof produces over 900 gallons of water, enough to fill more than three 275-gallon IBC tanks.
This guide covers everything you need to know to set up a reliable rain harvesting system using IBC tanks: legal considerations specific to the Midwest, sizing calculations, plumbing and filtration, connecting multiple tanks, and seasonal maintenance. Whether you want to water a backyard garden or irrigate a small farm, IBC-based rain harvesting is affordable, effective, and surprisingly easy to build.
Legal Considerations in the Midwest
Before building any rain harvesting system, verify that it is legal in your state and municipality. The good news for Midwest residents: Nebraska, Iowa, Kansas, Missouri, and South Dakota all allow residential rain harvesting with minimal restrictions. Nebraska has no state-level restrictions on rainwater collection for personal use, making it one of the most permissive states in the country.
However, some municipal codes may have rules about outdoor water storage containers, particularly regarding mosquito breeding, structural stability, and aesthetic standards. Omaha city code requires that outdoor water storage containers be covered to prevent mosquito breeding and that they do not create nuisance conditions. Check with your local code enforcement office before installing a large system, especially if it will be visible from the street.
For agricultural use on rural property, there are generally no restrictions in Nebraska. Farmers can harvest as much rainwater as they want for livestock, irrigation, and operational use. Some Nebraska Natural Resources Districts (NRDs) actually encourage rain harvesting as a water conservation practice and may offer technical assistance or incentive programs.
One important note: harvested rainwater in Nebraska is not approved for drinking water use without treatment meeting Safe Drinking Water Act standards. Use harvested water for irrigation, livestock, cleaning, and non-potable purposes unless you install an approved treatment system.
Capacity Calculations
The basic formula for rainwater collection is:
Collection efficiency accounts for losses from evaporation, splash, gutter overflow, and first-flush diversion. A well-designed system achieves 80-85% efficiency. Here are practical examples for Omaha-area conditions:
Omaha averages about 31 inches of rain annually, with peak months June-August. A single 275-gallon IBC connected to a 1,000 sq ft roof will fill 15-20 times per growing season.
System Components and Setup
A basic IBC rain harvesting system requires five components: a collection surface (your roof), gutters and downspouts, a first-flush diverter, the IBC tank(s), and an overflow outlet. Here is how each component works together.
Collection surface: Any impervious roof works -- asphalt shingles, metal, tile, or rubber. Metal roofs are ideal because they are smooth, non-porous, and do not shed granules or organic material. Avoid collecting from roofs treated with toxic coatings, zinc-coated metal (unless for non-plant irrigation), or roofs with heavy tree canopy overhead (excessive organic debris).
Gutters and downspouts:Standard residential gutters (5-inch K-style) handle most Midwest rainfall rates. Install gutter guards or screens to keep leaves and large debris out. Route the downspout to a diverter positioned above the IBC tank's top opening.
First-flush diverter: The first 10-20 gallons of runoff from any rain event carry the highest concentration of dust, pollen, bird droppings, and roof debris. A first-flush diverter captures this initial dirty water and diverts it away from your tank. Once the diverter chamber fills, clean water flows to the IBC. This single component dramatically improves water quality.
IBC tank positioning: Place your IBC tank on a level, stable surface. A full 275-gallon tank weighs over 2,400 pounds -- it needs solid support. Concrete pads, compacted gravel, or paver blocks work well. Elevating the tank on concrete blocks (even 6-12 inches) increases gravity pressure at the bottom valve, improving flow to drip irrigation or hose attachments.
Overflow: Every rain harvesting tank needs an overflow outlet near the top that directs excess water away from your foundation. Connect a bulkhead fitting near the top of the IBC to a pipe that routes overflow to a rain garden, swale, or storm drain. Without overflow management, water will pool around the tank base and potentially undermine its support.
Connecting Multiple IBC Tanks
One of the biggest advantages of IBC tanks for rain harvesting is scalability. Multiple IBCs can be connected in series or parallel to increase total storage capacity. Here are the two main connection methods:
Bottom-to-bottom connection (communicating vessels): Connect the bottom valves of adjacent tanks with a short section of pipe or hose. Water levels equalize between tanks automatically through gravity. This method is simple and ensures even fill across all tanks, but the connecting pipe must be large enough (2-inch minimum) to allow flow without restriction. All tanks must be at the same elevation.
Overflow cascade: Position the overflow outlet of the first tank to feed into the fill opening of the second tank, and so on. Water fills the first tank completely before cascading to the next. This method works even if tanks are at different elevations and allows you to draw from the cleanest water (first tank) while keeping sediment settled in the last tank.
For most residential systems, we recommend the overflow cascade method with 3-4 tanks. It is simpler to plumb, more forgiving of site conditions, and naturally creates a multi-stage settlement system where sediment drops out progressively. The last tank in the chain will contain the cleanest water.
Need tanks for your rain harvesting project? Our used IBC totes are perfect for this application. For rain collection, cosmetic condition does not matter -- a Grade B or C tank functions identically to a new one at a fraction of the cost. Check our rain barrel selection as well for smaller supplemental collection points.
Filtration and Water Quality
For garden irrigation, basic filtration is sufficient: gutter screens, a first-flush diverter, and an inline mesh filter on the output line. This prevents debris from clogging drip emitters while keeping the system simple and low-maintenance.
For livestock water, add a sediment filter (20-50 micron) and consider a UV sterilizer if animals will drink directly from the system. Livestock are less sensitive than humans to waterborne pathogens but can still be affected by heavily contaminated water.
For any system, keeping light out of the tank prevents algae growth. IBC tanks with white or translucent bottles will develop algae if exposed to sunlight. Paint the bottle black or wrap it in opaque material. This is one of the most common mistakes in IBC rain harvesting and it is easily prevented.
Seasonal Maintenance Calendar
Spring (March-April): Inspect tanks for winter damage. Clean gutters and replace gutter screens. Flush first-flush diverters. Reconnect any systems that were drained for winter. Check valve operation.
Summer (May-August): Monitor water levels. Clean inlet screens monthly. Check for mosquito breeding (ensure screens are intact and tanks are sealed). Drain and clean tanks if algae develops. This is peak collection and usage season.
Fall (September-October): Clear leaf buildup from gutters and screens. Assess total seasonal collection vs. usage to plan next year's capacity. Begin winterization planning.
Winter (November-February): Drain tanks if not using active freeze protection. Disconnect downspout diverters to prevent ice damage. Store removable filters indoors. Inspect tanks monthly for ice damage even when drained.
Getting Started: What to Buy
A complete single-tank rain harvesting system using a used IBC can be built for under $200 total. The tank itself (used Grade B) costs $60-100 from our inventory. Add a first-flush diverter ($20-40), a gutter diverter adapter ($10-15), an overflow bulkhead fitting ($8-12), and a garden hose adapter for the bottom valve ($10-15). Total materials: $108-182, providing 275 gallons of storage capacity.
Compare that to commercial rain harvesting systems that start at $400-800 for similar capacity but with less volume and more complicated installation. The IBC approach wins on cost, capacity, and simplicity. And when you are ready to expand, adding a second or third tank is straightforward and inexpensive.
Browse our IBC tote inventory to find the right tank for your rain harvesting project, or contact us if you need help choosing between sizes and conditions.