Complete Guide to IBC Rainwater Harvesting
IBC totes are one of the most cost-effective ways to collect and store rainwater. At 275 gallons per unit, they offer massive capacity in a compact, stackable footprint. This guide walks you through setup, Oklahoma-specific regulations, modifications, and ongoing maintenance.
Quick Math: How Much Rain Can You Collect?
Every 1 inch of rain on 1,000 sq ft of roof yields approximately 623 gallons of water. Oklahoma City averages 36 inches of rain per year. A modest 1,500 sq ft roof could theoretically collect 33,642 gallons annually— enough to fill over 122 IBC totes. Even capturing a fraction of that dramatically reduces irrigation water bills.
In This Guide
- 1Oklahoma Rainwater Harvesting Laws
- 2Choosing the Right IBC Tote
- 3Required Modifications
- 4Step-by-Step Setup
- 5Filtration & Water Quality
- 6Connecting Multiple Totes
- 7Seasonal Maintenance
1. Oklahoma Rainwater Harvesting Laws
Oklahoma is one of the most rainwater-friendly states in the country. The Water for 2060 Act (2012) explicitly encourages rainwater harvesting as part of the state's water conservation strategy. Key legal points:
Fully legal for residential properties. No permit required for non-potable use (irrigation, livestock, washing).
Permitted but may require local building permits for plumbing connections, especially if tying into building systems.
Not prohibited, but treatment systems must meet Oklahoma DEQ water quality standards if used for drinking.
Some HOAs may have aesthetic rules. IBC totes can be screened with fencing or privacy panels to comply.
2. Choosing the Right IBC Tote
Not all IBC totes are equally suitable for rainwater collection. Here is what to look for:
| Option | Suitability | Notes |
|---|---|---|
| Food-grade used (Grade A/B) | Excellent | Previously held food products; safe for garden irrigation |
| Reconditioned (new bottle) | Excellent | New clean bottle; best if previous contents are unknown |
| Non-food used | Use caution | Only if previous contents are known and non-toxic |
| Chemical-use history | Not recommended | Residual chemical contamination risk too high |
| New IBC tote | Overkill | Unnecessary expense for rainwater unless potable use planned |
At Oklahoma IBC, we always disclose previous contents on our used totes. For rainwater, we recommend food-grade Grade B units — they offer the best balance of safety, condition, and price (typically $50–$80).
3. Required Modifications
Converting a standard IBC tote for rainwater collection requires a few modifications:
Cut the top lid to accept your downspout and install a mesh screen (1/16" or finer) to block debris and mosquitoes.
Install a bulkhead fitting near the top to divert overflow away from your foundation when the tote is full.
Block sunlight to prevent algae growth. Use an IBC cover, wrap with UV-blocking material, or paint the bottle (exterior only).
Replace the 2" butterfly valve with a garden-hose-compatible 3/4" brass spigot for easy connection.
Diverts the first few gallons of roof runoff (containing the most debris and contaminants) before water enters the tote.
Raising the tote 12-24 inches on cinder blocks or a platform provides gravity pressure for garden hoses.
Total modification cost:$85–$260 depending on components. Combined with a used IBC at $50–$80, your complete 275-gallon rainwater system costs $135–$340— far less than a comparable commercial rain barrel system.
4. Step-by-Step Setup
- 1
Choose Location
Place near a downspout on level ground. Ensure the surface can support ~2,425 lbs (full weight). A concrete pad or compacted gravel base works best.
- 2
Build or Place Platform
Elevate the IBC 12-24 inches for gravity-fed water pressure. Use cinder blocks, a timber frame, or concrete blocks. Verify level.
- 3
Prepare the Inlet
Cut or modify the top lid to accept your downspout. Install the mesh screen over the opening. Seal around the downspout connection to prevent mosquito entry.
- 4
Install Overflow
Drill and install a bulkhead fitting 2-3 inches below the top of the tote. Connect a hose or pipe directing overflow away from structures and toward a garden bed or drain.
- 5
Install Spigot
Replace or adapt the existing 2" valve to a garden-hose-compatible spigot. Use Teflon tape on all threaded connections.
- 6
Add Light Blocking
Wrap the tote with an opaque cover, burlap, or paint the exterior. Algae grows rapidly in translucent containers exposed to sunlight.
- 7
Connect Downspout
Route the downspout into the inlet opening. Use a first-flush diverter upstream if you have one. Test the system with a garden hose before the next rain.
5. Filtration & Water Quality
Roof runoff contains dust, pollen, bird droppings, and trace amounts of roofing material. For garden irrigation, basic filtration is adequate. For any human-contact use, additional treatment is needed.
| Intended Use | Minimum Filtration |
|---|---|
| Garden irrigation | Inlet screen + first-flush diverter |
| Livestock watering | Inlet screen + sediment filter (50 micron) |
| Toilet flushing / laundry | Sediment filter + carbon filter |
| Potable (drinking) | Sediment + carbon + UV sterilizer + DEQ testing |
6. Connecting Multiple Totes
For larger capacity, IBC totes can be linked together. The simplest method is connecting the overflow of one tote to the inlet of the next, creating a series system. Alternatively, connect them at the bottom with a manifold pipe so water levels equalize across all totes.
Simpler setup. First tote fills completely before water flows to the next. Uneven fill levels. Good for 2–3 totes.
All totes fill evenly. Requires level placement and 2" PVC manifold at valve height. Best for 3+ totes or gravity-feed systems.
Three linked IBC totes provide 825 gallons of storage — enough to irrigate a 2,000 sq ft garden through a two-week Oklahoma dry spell. Check out our accessories for linking kits and adapters.
7. Seasonal Maintenance
A well-maintained IBC rainwater system lasts years with minimal effort. Follow this seasonal schedule:
Inspect and clean inlet screens. Flush totes if stagnant over winter. Check all connections for leaks. Clean first-flush diverter.
Monitor algae growth monthly. Ensure light-blocking cover is intact. Check water level and use stored water regularly to prevent stagnation.
Clear gutters and downspouts of leaves. Clean inlet screens after leaf drop. Top off totes before winter if using for freeze-season livestock water.
Drain totes to 80-90% capacity to allow freeze expansion. Disconnect and drain hoses. In hard freeze zones, consider draining completely or insulating.
Ready to Start Harvesting Rainwater?
We carry food-grade used IBC totes ideal for rainwater collection, plus all the accessories you need.